Methods and apparatus for communicating changes between a user interface and an executing application using property paths

ABSTRACT

In one aspect the invention relates to a method of associating an element of a user-interface to a current state of a property in a system including an application having a plurality of components, wherein at least one component has a property, wherein each property is identified with an identifier. The method comprises associating the element of the user-interface with a property path, the property path including a concatenation of a plurality of identifiers, the concatenation of identifiers defining a path through the components of the application to a property at the end of the concatenation, and mapping the property path to a current state of the property at the end of the path defined by the concatenation of identifiers, to associate the element of the user-interface with the current state of that property.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to the co-pendingU.S. Provisional Application, Ser. No. 60/254,995, filed Dec. 12, 2000,entitled “Methods And Apparatus For Interactive Thin-Client ApplicationsUsing Property Paths,” the entirety of which is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to client-server networks and, inparticular, to methods and apparatus for associating an element of auser-interface to a current state of a property.

BACKGROUND OF THE INVENTION

Contemporary computer networks consist of a number of computer systems,called nodes, communicating with other computer systems viacommunication links. Typically, some of the nodes are client nodes andother nodes are server nodes. A client node formulates and deliversqueries to a server node. A user of the client node enters the queriesthrough a user-interface operating on the client node. The server nodeevaluates the queries and delivers responses to the client node fordisplay on the client user-interface.

Usually, the server nodes host a variety of application programs orprocesses that can be accessed and executed by client nodes. When aclient node launches an application program, the execution of thatapplication program can occur at either the client node or the servernode, depending upon the computing model followed by the computernetwork.

In a client-based computing model, the application program is packagedand sent down to, or pre-installed on, the client node, allowing theclient node to run the application using the resources of the clientnode. This approach has several drawbacks. First, the client node musthave sufficient memory, disk space, and processing power to effectivelyexecute the application. A related problem that occurs using this modelis that the number of applications a given client is able to execute islimited due to client resource constraints. Further, applications builtthis way are complex to develop and maintain and typically requiremodification or “porting” for all supported client computer systemtypes. Moreover, this technique exacerbates the administration burden ona network administrator.

In a server-based computing model, the server node executes theapplication program, and only the control information for the clientuser-interface is transmitted across the computer network to the clientnode for display. Using this approach, user-interface events must besent between the client and the server in order for the serverapplication to process the events. This may result in perceived delaysof user-interface response. Further, the application program must bespecifically written, or changed, to support the user-interface on theclient node. This increases the complexity of the application andprevents this technique from being useful with off-the-shelfapplications.

A refinement of the server-based model is to supplant the device driverto which the application communicates in order to send screen and deviceupdates back and forth between the client and the server. This approachavoids requiring applications to be rewritten. However, this approachrequires device information to be sent between the client and the serverin order to maintain the client display, again introducing perceivedlatency into the interface. Further, server-side processing requirementsare increased in order to satisfy resulting device information requiredfor communication with each connected client.

A recent, further refinement of the server-based model is to deploy theuser-interface portion of the application as a mark-up language documentsuch as Hyper Text Markup Language (HTML) document. However in usingthis approach, information sent from the server application to theclient begins to “age” immediately. In other words the information maychange on the server but the client would not automatically be notifiedand updated. Further, with this approach, interactivity requires contextswitching between pages even to perform simple tasks.

Standard and emerging approaches to application development for Webapplication delivery rely on one of two approaches. The first approachis adapting ‘page based’ application delivery code (e.g., servlets) tomore dynamic use (e.g., sequence of servlets). The second approach iswiring user-interface components to server components. The firstapproach has the advantage of remaining Web-centric and within the skillset of Web developers, but is limited by its page-based roots.Generating applications with a user-interface using several pages (ordialogues) typically requires coordinating the server-side components togenerate each page on an individual basis. This coordination becomesvery difficult as the number of pages or the number of clientsincreases. The second approach, wiring, still requires the applicationdeveloper to deal with the dynamic aspects of the application, as adeveloper must wire to existing object instances that the wiring toolknows about. This is typically objects that exist at application startup, or at other well defined times. The second approach typicallyrequires customized tools to perform all aspects of UI design, includinglayout and formatting.

SUMMARY OF THE INVENTION

The present invention avoids these shortcomings. The present inventionprovides a mechanism by which the user-interface portion of theapplication can be delivered to the computer user either on the samemachine on which the application is executing or on another machineremote from the machine executing the application. The inventionseparates the user-interface from the underlying application enablingthe design of the user interactive portion of the application to berelatively straightforward.

The invention also permits the user interactive portion to be deployedon a wide range of client hardware environments without bringing with itall the required logic for performing the functionality of a particularapplication. These features give the user the effect of directlyinteracting with the application even though the application ispotentially running somewhere else. User-interface, event handling andscreen rendering logic stay on the client, thus dramatically reducingnetwork traffic and latency. The invention also allows theuser-interface portion to be connected with objects that do notcurrently exist, but may exist in the future. This makes it easier tospecify connections. The invention connects the user-interface toobjects using property paths. Property paths represent abstract pathsand this abstract quality allows the UI to be connected to objects thatmay exist in the future but that do not exist at application startup orany other well defined point in time.

In one aspect the invention relates to a method of associating anelement of a user-interface to a current state of a property in a systemincluding an application having a plurality of components, wherein atleast one component has a property, wherein each property is identifiedwith an identifier. The method comprises associating the element of theuser-interface with a property path, the property path including aconcatenation of a plurality of identifiers, the concatenation ofidentifiers defining a path through the components of the application toa property at the end of the concatenation, and mapping the propertypath to a current state of the property at the end of the path definedby the concatenation of identifiers, to associate the element of theuser-interface with the current state of that property. In anotherembodiment, the method includes a) examining each identifier in theconcatenation of the property path in succession, b) determining, forthe first identifier in the concatenation of the property path, a secondstate of a property with a name identical to the first identifier, acomponent of the application containing that property becoming a rootapplication component; c) identifying, for the first identifier, acomponent of the application to which the second state points as acurrent application component, d) mapping the first identifier to thesecond state, e) determining for the next identifier in theconcatenation of the property path, a next state of a property with aname identical to the next identifier located within the currentapplication component, f) identifying, for the next identifier, acomponent of the application to which the next state points as a currentapplication component, g) mapping the next identifier to the next state,and h) repeating steps e, f and g until the last identifier of theconcatenation is examined to map the property path to the current stateof the property with a name identical to the last identifier. In anotherembodiment, the method includes mapping the property path to anundefined state if no property is found that corresponds to anidentifier in the plurality of identifiers in the concatenation.

In another embodiment, the method includes generating a node tree havinga plurality of nodes, wherein each node of the node tree represents amapping of an identifier to one of, a state of a property and anundefined state. In another embodiment, the node tree represents aplurality of property paths. In another embodiment, the method includesmonitoring a plurality of states within the application to detect achange in one of the states of the plurality of states, each state inthe plurality corresponding to one of the states mapped to an identifierin the concatenation of the property path. In another embodiment, themethod includes receiving a property change event from aJAVABEAN-compatible component.

In another embodiment, the method includes re-mapping the property pathto a new current state in response to detecting the change in one of thestates of the plurality of states. In another embodiment, the methodincludes re-mapping the identifier the concatenation of identifiers tothe changed state in response to detecting the change in one of thestates of the plurality of states. In another embodiment, the methodincludes generating a property change message in response to a change ina state of a property corresponding to one of the identifiers in theconcatenation of the property path. In another embodiment, the methodincludes updating one or more user-interface elements associated withthe property path with a new current state in response to a change inthe current state of the property.

In another embodiment, the method includes, a) detecting a change in oneof a plurality of states in an application, each state in the pluralitycorresponding to one of the states mapped to an identifier in theconcatenation of the property path, b) examining each identifier in theconcatenation of the property path in succession, starting with anidentifier corresponding to the changed one of the states of theplurality of states, c) determining for a currently examined identifier,a new next state of a property with a name identical to the currentlyexamined identifier, d) re-mapping the currently examined identifier tothe new next state in response to a change in a currently mapped state,and e) repeating steps c and d for each subsequent identifier in theconcatenation of identifiers. In another embodiment, the method includesterminating the repeating in response to the new next state beingidentical to a state currently mapped for that currently examinedidentifier. In another embodiment, the method includes monitoring a newplurality of states within the application, the new plurality includingthe new next states mapped to an identifier in the concatenation of theproperty path.

In another embodiment, wherein the property path is a first propertypath and the concatenation of identifiers includes a wildcardidentifier, the method includes mapping a second property path to afirst value, and determining a second value for the wildcard identifierin response to the first value mapped to the second property path. Inanother embodiment, the method includes determining the second valuesuch that replacing the wildcard identifier of the first property pathwith the second value causes the current state mapped to the firstproperty path with the replaced wildcard identifier to be equal to thevalue mapped to the second property path. In another embodiment, themethod includes dynamically binding the property path to one of theapplication components including the property corresponding to thecurrent state mapped to that property path.

In another embodiment, the method includes transmitting to theapplication a request to update the current state of the property mappedto the property path associated with the element of the user-interfacein response to a user modification of the value. In another embodiment,the method includes inhibiting a property change message in response tothe application updating the current state of the property in responseto the request to update. In another embodiment, wherein the userinterface comprises an exemplary element associated with a property pathincluding a wildcard identifier, the wildcard identifier correspondingto an indexed property including an index value range from a minimumvalue to a maximum value, the method includes generating an additionalelement for each index value of the indexed property from the minimumvalue to the maximum value by copying the given element associated withthe property path, and associating a new property path with eachadditional element. In another embodiment, the method includes replacingthe wildcard identifier associated with the given element with thecorresponding index value of the additional element to define the newproperty path. In another embodiment, the method includes registeringinterest in the property path. In another embodiment, the methodincludes mapping one of the identifiers in the concatenation of theproperty path to a state of a property corresponding to the one of theidentifiers.

In another embodiment, the invention relates to a system for associatingan element of a user-interface to a current state of a property of anapplication, wherein the application has a plurality of components, atleast one component having a property and each property is identifiedwith an identifier. The system includes a property connector module toidentify an association between the element of the user-interface and aproperty path, the property path including a concatenation of aplurality of identifiers, the concatenation of identifiers defining apath through the components of the application to a property at the endof the concatenation, and to map the property path to a current state ofthe property at the end of the path defined by the concatenation ofidentifiers, thereby associating the element of the user-interface withthe current state of that property. In another embodiment, the systemincludes a client node. The client node includes the user interfacehaving one or more elements, and a client portion of the propertyconnector module. In another embodiment, the system includes a servernode. The server node includes the application, and a server portion ofthe property connector module.

In another aspect, the invention relates to a method for creating auser-interface independently of an application with which the userinterface interacts, wherein the application includes a plurality ofcomponents and at least one component contains a property, wherein eachproperty is identified with an identifier. The method includes insertingat least one element into the user-interface, and associating at leastone property path with one inserted element, the property path includinga concatenation of a plurality of identifiers, the concatenation ofidentifiers defining a path through the components of the application toa property at the end of the concatenation. In another embodiment, themethod includes determining a list of property paths associated with theapplication, and selecting the property path from the list to associatewith the one inserted element of the user-interface from the list ofproperty paths.

In another embodiment, the method includes receiving a property pathdescription file associated with the application, the property pathdescription file including a plurality of identifiers associated withthe application and a relationship between the plurality of identifiers.

In another embodiment, the method includes executing the application,and interacting with the executing application to determine a pluralityof identifiers associated with the application and a relationshipbetween the plurality of identifiers. In another embodiment, the methodincludes transmitting a request to register for a property changemessage corresponding to the property path associated with the elementof the user-interface. In another embodiment, the method includesproviding at least one predefined element, and enabling selection fromthe at least one predefined element to insert the selected predefinedelement into the user-interface. In another embodiment, the predefinedelement comprises one of an image type user-interface element, aniterator type user-interface element, a text type user-interfaceelement, a hidden type user-interface element, a value typeuser-interface element, a slider type user-interface element, a treeviewtype user-interface element, a button type user-interface element, aniframe type user-interface element, a tab type user-interface element, aflipflop type user-interface element, a deck type user-interfaceelement, a dropdown type user-interface element, a radio typeuser-interface element, and a script type user-interface element.

In another aspect, the invention relates to a system for creating auser-interface independently of an application with which the userinterface interacts, wherein the application includes a plurality ofcomponents and at least one component contains a property, wherein eachproperty is identified with an identifier. The system includes aproperty connector module to insert at least one element into theuser-interface, and to associate at least one property path with oneinserted element, the property path including a concatenation of aplurality of identifiers, the concatenation of identifiers defining apath through the components of the application to a property at the endof the concatenation. In another embodiment, the system includes aclient node. The client node includes the user interface having one ormore elements, and a client portion of the property connector module. Inanother embodiment, the system includes a server node. The server nodeincludes the application, and a server portion of the property connectormodule.

In another aspect, the invention relates to a method using a systemhaving an application comprising one or more objects, with at least oneobject including one or more properties. The method associates auser-interface element, which is independent of the application, with aproperty of the application. The method includes executing a processthat is independent of the application; representing a property of theapplication by a property path and associating, by theapplication-independent process, the user-interface element with theproperty path. This associates the user-interface element with theproperty of the independent application. In one embodiment, the methoddetermines whether a property of an object of the application existsthat corresponds to the property path. In another embodiment, thedetermining process includes employing a value of a second propertycorresponding to a second property path (e.g., cross-mapping).

In another embodiment, the method includes monitoring a state of theproperty and detecting a change in the state of the property. In anotherembodiment, the process of detecting includes receiving a propertychange event from an API of a JAVABEAN™ compatible component. In anotherembodiment, the method includes updating the user-interface element inresponse to detecting the change in the state of the property. Inanother embodiment, the method includes generating a property changemessage in response to detecting the change in the state of therepresented property. In another embodiment, the method includesregistering for a property change message for the property representedby the property path. In another embodiment, the method includesdetecting a change in a state of one or more properties along theproperty path, and responding to a detected change in a value that theproperty path represents.

In another embodiment, the method includes determining at least oneproperty path associated with the application and selecting the propertypath to associate with the user-interface element from at least onedetermined property path. In another embodiment the process ofdetermining at least one property path includes traversing from a rootobject of the application to a corresponding property, using objectpointers. In another embodiment, this includes mapping the traversalfrom a root object of the application to the corresponding property. Inanother embodiment, the process of mapping includes generating a nodetree. In another embodiment, the method includes indicating which nodesin the node tree correspond to a property path that the client hasregistered interest in. In another embodiment, the method includesdynamically binding the property path to the object containing therepresented property.

In another embodiment, the method includes allowing a user to modify avalue associated with the user-interface element and updating theproperty of the application represented by the property path associatedwith the user-interface element in response to a user modification ofthe value associated with the user-interface element. In anotherembodiment, the method includes inhibiting a property change message inresponse to updating the property of the application in response to theuser modification.

In another aspect, the invention relates to a method using a server nodehaving an application comprising a plurality of objects, with eachobject including one or more properties, the method indicating aproperty of the application to monitor. The method includes executing aprocess that is independent of the application, representing a propertyof the application by a property path and receiving, by theapplication-independent process, a request to register for a propertychange message associated with a property path to indicate the propertyof the independent application to monitor. In one embodiment, thismethod includes determining whether a property of an object of theapplication exists that corresponds to the property path. In anotherembodiment, the process of determining includes employing a value of asecond property corresponding to a second property path (e.g.,cross-mapping).

In another embodiment, the method includes monitoring a state of theproperty and detecting a change in the state of the property. In anotherembodiment, the process of detecting includes receiving a propertychange event from an API of a JAVABEAN™ compatible component. In anotherembodiment, the method includes transmitting the changed state inresponse to detecting the change in the state of the property. Inanother embodiment, the method includes generating a property changemessage in response to detecting the change in the state of theproperty. In another embodiment, the method includes registering theproperty change message of the request for the property represented bythe property path.

In another embodiment, the method includes determining at least oneproperty path associated with the application. In another embodiment,the process of determining at least one property path includestraversing from a root object of the application to a correspondingproperty by using object pointers. In another embodiment, the methodincludes mapping the traversal from a root object of the application tothe corresponding property. In another embodiment the process of mappingincludes generating a node tree. In another embodiment, the methodincludes indicating which nodes in the node tree correspond to aproperty path the client has registered interest in. In anotherembodiment, the method includes dynamically binding the property path tothe object containing the represented property.

In another aspect, the invention relates to a method using a client nodehaving a user-interface, including one or more elements, that isindependent of an application, the method creating a user-interfaceelement. The method includes executing a process independent of theapplication, employing an element of the user-interface, representing aproperty of the application by a property path and selecting, with theapplication-independent process, the property path or paths to associatewith the user-interface element. In one embodiment, the method includestransmitting a request to register for a property change messageassociated with the selected property path.

In another embodiment, the method includes receiving the property changemessage in response to a change in a state of the property representedby the property path. In another embodiment, the method includesupdating the user-interface element in response to notification of thechange in the state of the property. In another embodiment, the methodincludes receiving at least one property path associated with theapplication. In another embodiment, the method includes allowing a userto modify a value associated with the user-interface element andtransmitting the modified value and the associated property path. Inanother embodiment, the method includes inhibiting a property changemessage in response to transmitting the modified value associated withthe user-interface element.

In another aspect, the process of employing an element includesproviding to the user at least one predefined element for theuser-interface, enabling the user to select from at least one predefinedelement for the user-interface and employing the selected predefinedelement. In another embodiment, the predefined element includes one ormore of the following: displaying a property value as a piece of text,allowing the displayed property value to be edited, enabling a buttonthat may be disabled based on the property value, vertical andhorizontal sliders for numeric properties, displaying an image dependenton a property value, displaying an embedded frame dependent on aproperty value, an anchor dependent on a property value, ability to hideor show part of the UI dependent on a property and expression and theability to change the style of part of a UI dependent on a property andexpression. In another embodiment, the predefined element includes oneor more of the following: selections of displaying one of a ‘deck’ of UIfragments dependent on a property value, a dropdown menu where eachchoice is a value from an range of indexed properties, one tab permember of a range of indexed properties, a set of radio buttons, atreeview based on property paths and the ability to repeat part of a UIonce for each member of a range of indexed properties.

Some objects of this invention are as follows: to allow simple UIdevelopment for developers with little or no programming experience; toallow strong separation between application and UI development; to allowseparation of UI static and dynamic aspects; to have low bandwidth andlatency-tolerance communications; to allow device-clients to be tailoredto the devices' capabilities; to require only a small learning curve forapplication and UI developers; and to allow for scalable servers.

To accomplish some of these objects, the invention includes a system forproviding rich/highly interactive client interfaces to applicationsrunning on a centralized server (or servers). A key part of the systemis that the interface between client and server is highly abstract andit can function with both other client types (other Web browsers anddevice specific clients) and other server types (e.g., COM).

The system uses a ‘loose’ coupling mechanism, which allows theserver-side application to be designed with little regard for theuser-interface. By maintaining this strong separation it is possible fora user-interface to be completely redesigned without access to theapplication code, or the infrastructure supporting it. For example athird party could generate a user-interface for a ‘published’application without any access to the application code or runtimeenvironment. The system also allows one application and the server onwhich it is located to be used with many different types ofuser-interfaces. New client types may be designed and deployed withouttouching the server code. A third party could design a new client typewithout the server's involvement. The user-interface for a particularapplication can be changed or ported to a new device without having toeven stop the server application, let alone redesign or rebuild it. Thisis the ‘number one want’ on a recent survey of Web applicationdesigners. The user-interface can be tuned or given a new look and feelwithout disrupting the function of the application. This may be doneusing standard tools. As the user-interface is strongly separated fromthe server, different user-interfaces can be developed for differentdevice capabilities. There is no intention that user-interfaces ondifference clients should look identical. This simply makes it mucheasier to develop a client ‘player’ for a new device

The system takes advantage of the fact that most user-interfaces areessentially static. A large portion of a user-interface does not changeat all. A typical example is a form. The form itself is not modifiedduring execution, but only the values that appear in the fields of theform. The dynamic aspect of a user-interface generally consists ofchanges to the static page ‘template’ such as filling in fields,changing text values and a navigation through a number of dialogs orpages under the control of the user and/or the application. For aWeb-client, the static aspects of a user-interface generation, and thenavigation aspects (under user control) are already well understood byusers and developers alike. Rather than replace these with differentnotions, the invention keeps standard Web-metaphors. The invention addsonly the ability to fill in a page template dynamically.

By keeping the interface between application and user-interface verysmall, and by separating the static and dynamic aspects of a UI, theinvention allows the static aspect of a user-interface to be developedusing standard UI development tools. These tools can be extended (oradditional tools provided) to add the dynamic aspect of the UI. Becauseof the approach taken to the static/dynamic split, this is extremelystraightforward for the UI developer. A unique aspect that the systembrings to UI technology is the way in which dynamic aspects of theapplication (e.g., creation of new objects, changes in values) may bereflected in a static user-interface by linking UI elements.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of the embodiments of the invention, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages will occur to those skilled inthe art from the following description of a preferred embodiment and theaccompanying drawings, in which:

FIG. 1 is a block diagram of an embodiment of property path associationsconstructed in accordance with the invention;

FIG. 2 is a block diagram of an embodiment of the sub-components of theproperty connector API of FIG. 1 constructed in accordance with theinvention;

FIG. 3 is a block diagram of another embodiment of the systemarchitecture of the invention;

FIG. 4 is a screenshot of a UI development application that is beingexecuted in combination with an embodiment of the client portion of theinvention;

FIG. 5 is a screenshot of a UI application illustrating an embodiment ofthe invention during execution;

FIG. 6 is a block diagram of an embodiment of the mapping of registeredproperty paths of the invention;

FIG. 7 is a flow diagram of an embodiment of client and serverinteraction constructed in accordance with the invention; and

FIG. 8 is a block diagram of another embodiment of the server portionwith an extension feature according to the invention

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a block diagram of an embodiment of a system 10 forcommunicating changes between a user-interface and an executingapplication, using property paths. The system 10 includes a serverprocess 14, a client process 18 and a property connector API 22. Theserver process 14, the client process 18 and the property connector API22 can be located on a single computing device or distributed amongseveral computing devices. The server process 14 includes an application26 with application components 34 a, 34 b, 34 c and 34 d (generally 34).In this embodiment, the application components 34 a, 34 b, 34 c and 34 dare instances of objects that the application 26 generates.

Each of the application components 34 a, 34 b, 34 c and 34 d includeszero or more properties Ace 38 a, 38 b, 38 c, 38 d, 38 e and 38 f(generally 38). This embodiment includes two types of properties. Afirst type of properties 38, for example, 38 d, 38 e and 38 f, have avalue for a specific variable. A second type of properties 38, forexample, 38 a, 38 b and 38 c, have a pointer to another applicationcomponent 34 (e.g., object, class), thus this second type of property 38represents a composite of additional application components 34 and theirproperties 38. In other embodiments, application components 34 can begenerated by a process using a data file. For example, applicationcomponents 34 can be representations of nodes within a structured datafile, such as XML or a database, where the properties 38 are attributesspecified in the structured file or associated document type definition(“DTD”) (i.e., a specific definition that follows the rules of theStandard Generalized Markup Language). In another embodiment, theapplication components 34 support additional standard properties 38 suchas ‘parent’, ‘child[i]’, and the like.

Many applications 26 are object-oriented and as such, generate astructured relationship between the objects 34. The structuredrelationship can be illustrated as a node tree. The root node is thefirst object of the application and each object that the root objectpoints to becomes a child node. Each object that the child node pointsto becomes a grandchild node and so on. For example, object 34 arepresents a root node. Objects 34 b and 34 c are children nodes of theroot node 34 a. Object 34 d is the child node of object 34 c and thegrandchild node of object 34 a. Each part of the application 26 state(i.e., values of application component properties 38 at a particularinstant in time) is accessible via a traversal of a ‘path’ from one ormore root objects to the state of a property itself by following objectpointers (e.g., properties 38 a, 38 b, 38 c). This path taken by thetraversal of the structured relationship is a property path, alsoreferred to as a pathname, and is described in more detail below. Anobject and/or property may be addressable by several ‘paths’ from theroot node, for example, an object representing an Employee may beaccessible as ‘the current employee’ (root->current), the 10^(th)employee in an index (root->index->item 10), the manager of some otheremployee (root-> . . . ->manager) and the like. These paths correspondto different concepts that happen to have the same object as theircurrent value.

Some models for application development (e.g., JAVABEANS™ componentarchitecture by Sun Microsystems, Inc. of Palo Alto, Calif. and ACTIVEX™platform by Microsoft Corporation, Redmond, Wash.) provide a linkbetween the application components 34 of an application 26 by using aproperty-based link. A property-based link is an object pointer that isaccessible via a standard means (e.g., ‘get’ and ‘set’ methods).Applications 26 using property-based links undertake to inform theserver process 14 about changes in the property-based link using, forexample, property change events.

The client process 18 produces a user-interface (“UI”) 42 that isdisplayed to a user. The UI 42 includes one or more user-interfaceelements 46 a and 46 b (generally 46). The UI 42 can be, for example, aWeb page, an HTML document, a custom UI and the like. Though the UI isgenerally hereinafter referred to as a page 42, this should be withoutloss of generality as the UI 42 can be displayed on a non-Web clientusing a native language. The UI elements 46 are associated with one ormore values 50 a, 50 b, 50 c (generally 50) that the UI elements 46display or make decisions in response thereto. The user-interfaceelement 46 is a portion of the UI 42 that dynamically changes and isassociated with a state of property 38 of an application component 34.As described in more detail with FIG. 4, a user of the page 42associates each of the UI elements 46 to the one or more properties 38of an application component 34 by indicating one or more property paths.The UI element 46 can be, for example, an input box for textual ornumerical input and display of a value of a property 38. The UI element46 also can be, for example, a horizontal slider for numerical input anddisplay of a value of a property 38. As shown, the first user-interfaceelement 46 a displays and/or affects a value 50 a associated with astate of a property 38 of one of the application components 34. Thesecond user-interface element 46 b displays and/or affects two values 50b and 50 c.

Between the application components 34 and the user-interface elements 46is the property connector API 22. The property connector API 22 includesa client portion 22 a and a server portion 22 b. The property connectorAPI 22, and thus the client portion 22 a and the server portion 22 b, isa process that is independent of the application 26 (i.e., not a part ofnor generated from the application 26). The property connector API 22process can be implemented as software, as hardware or as a combinationof both. The execution of the property connector API 22 can be initiatedin several ways. A computing device on which the property connector API22 resides can initiate execution of the property connector API 22 uponpower up or upon a authorized user log-in. The computing device caninitiate execution of the property connector API 22 when the computingdevice downloads a page 42 containing UI elements 46 associated withproperty paths. The computing device can initiate execution of theproperty connector API 22 when the user initiates execution of theapplication 26 or requests delivery of the page 42. In one embodiment,when the computing device initiates execution of the property connectorAPI 22, the computing device also receives a startup argument includingthe name of a file containing the UI page 42 details, and details of theserver node 60 to connect to and the application 26 to start.

As explained in more detail below, the property connector API 22 mapseach dynamic user-interface element 46 to a property 38 of anapplication component 34 using the associated property path. Theproperty path defines the interaction between the client process 18 andthe server process 14 in terms of properties 38 of the application 26rather than in terms of the user-interface elements 46.

In its mapping, the property connector API 22 represents a property 38of an application component 34 within an application 26 as a propertypath. The property path is the concatenation of one or more identifiers.An identifier corresponds to a property 38 within an applicationcomponent, which can be a value or a pointer. The property path definesa path through the application 26 from a root component 38 to theparticular application component 34, and a property 38 itself of thatapplication component. For example, property 38 a points to applicationcomponent 34 c and the property 38 c of application component 34 cpoints to application component 34 d that contains property 38 d. Theproperty path that corresponds to the property 38 d in this example is‘App.PropertyID1.PropertyID3.PropertyID4’.

Each part of the property path (i.e., App, PropertyID1, PropertyID3,PropertyID4) is an identifier. The property connector API 22 uses theseidentifiers to traverse the path in the application 26 defined by theproperty path. The ‘App’ identifier identifies the root node. The‘identifies the property 38 a within the root component 34 a andproperty 38 a points to application component 34 c. The propertyconnector API 22 determines the value of ‘PropertyID1’ by obtaining thepresent state (i.e., value) of a property with the same name within theroot component of the application 26 identified by ‘App’. For example,the property connector API 22 determines the value by using a ‘get’method of an API for the application 26. The property connector API 22determines the present state points to the application component 34 c.Because the value of property corresponding to identifier ‘PropertyID1’is component 34 c, the ‘PropertyID3’ identifier identifies the property38 c within the component 34 c. The property connector API 22 determinesthe value of ‘PropertyID3’ by obtaining the present state (i.e., value)of the property 38 c with the same name within the component 34 c, whichwas identified using ‘PropertyID1’, The property connector API 22determines the present state points to the application component 34 d.Because the value of property corresponding to identifier ‘PropertyID3’is component 34 d, the ‘PropertyID4’ identifier identifies the property38 d within the component 34 d. The property connector API 22 determinesthe value of ‘PropertyID4’ by obtaining the present state (i.e., value)of the property 38 d with the same name within the component 34 d, whichwas identified using ‘PropertyID3’. Property 38 d is not a pointer, buta number, for example, salary. The property connector API 22 maps thecurrent state of this property 38 d to the property path‘App.PropertyID1.PropertyID3.PropertyID4’. While mapped, the propertypath ‘App.PropertyID1.PropertyID3.PropertyID4’ has the value of thesalary of property 38 d.

Property paths are not “wired” connections from a user-interface element46 to the associated application component 34, but more analogous to adescription of what ‘type’ of data the user-interface can display and/oraffect (i.e., a loosely coupled, flexible connection). This means thatduring execution, the application 26 can create or delete applicationcomponents 38 without any adverse affect on the user-interface elements46. For example, the property path‘App.PropertyID1.PropertyID3.PropertyID4’ corresponds, at one point intime, to property 38 d, as stated above. However, if the application 26changed property 38 c, ‘PropertyID3’, to subsequently point toapplication component 34 b, instead of application component 34 d, theproperty path ‘App.PropertyID1.PropertyID3.PropertyID4’ subsequentlycorresponds to property 38 e, not property 38 d. When notified of thechange, the property connector API 22 updates the value 50 of theuser-interface element 46 associated with the property path‘App.PropertyID1.PropertyID3.PropertyID4’ to reflect the current stateof property 38 e.

In another example, for a human resources application, the property pathto the “salary” property of the twenty-seventh employee in a list ofemployees of a certain department is ‘HRApp.Dept.Employee[26].Salary’(counting from 0). The property path describes an abstract property ofthe application 26 as a whole, not a specific property of a particularinstantiated object. In other words, if the user-interface element 46was to be associated with a specific property, then the path could besimply, for example, ‘property 38 d’. Then regardless of whichcomponents 34 pointed to which other components 34 would not matter,because the property path would always reflect the state of property 38d. This, however, is not how property paths work. The property pathidentifies a path through the application 26 and not one specificproperty 38 d located in the application 26. The path can change as oneof the properties 38 corresponding to one of the identifiers in theconcatenation changes. When a component 34 changes and points to adifferent component, the property path follows that change and theproperty path reflects the state of the new property the path now endsat.

Similarly, a property path can also represent a property with apotential to exist, but that does not exist at the present time. Forexample, if the list of employees only contains twenty-six employees(numbered 0 to 25), the property path ‘HRApp.Dept.Employee[26].Salary’does not correspond to any property. When another employee is added, theproperty path ‘HRApp.Dept.Employee[26].Salary’ would then point to thesalary property of the twenty-seventh employee. This example illustrateshow property paths can be used to describe properties that do not existpresently, but can exist in the future, in addition to those propertiesthat exist only at application startup, or at some other well definedpoint. In the human resources application example, this means that asthe list of employees change, the actual employee who is twenty-seventhin the list of employees can change, but the property path remainspointing to the salary property of the twenty-seventh employee,regardless of who that may be. This method of using the structuredrelationship between application components 34 to create a property pathis important in allowing strong separation between UI elements 46 andapplication components 34.

Using this example in connection with FIG. 1, the second value 50 c ofUI element 46 b displays the salary of the twenty-seventh employee of aspecific department because the value 50 c is associated with theproperty path ‘HRApp.Dept.Employee[26].Salary’. The client portion 22 amaps this association between the value 50 and the property path. Theserver portion 22 b maps the same property path‘HRApp.Dept.Employee[26].Salary’ to the property 38 d of applicationcomponent 34 d. To obtain this mapping, the server portion 22 b followsthe pointers with the application components 34 that correspond to theproperty path. In one embodiment, the server portion 22 b follows thepointers by using ‘get’ methods and constructing a structure tree map160 (FIG. 6).

The ‘HRApp’ portion of the property path corresponds to the application26 and the first created application component 34 a (i.e., the rootapplication component). The ‘Dept’ portion of the property pathcorresponds to the property 38 a that points to the applicationcomponent 34 c, which in this example represents a list of employees ofthe indicated department. The ‘Employee[26]’ portion of the propertypath corresponds to the property 38 c that points to the Ads applicationcomponent 34 d, which in this example represents information about thetwenty-seventh employee. The ‘Salary’ portion of the property pathcorresponds to the property 38 d that contains a value, which in thisexample represents the amount of the salary of the twenty-seventhemployee. The application component 34 d can also contain otherproperties (not shown) that have values representing information aboutthat particular employee, such as name, social security number, date ofhire and the like.

As the list of employees for the indicated department changes, theproperty 38 c that pointed to application component 34 d changes andsubsequently points to another application component (not shown). Inthis example, before the change, the application component 34 drepresented information about the twenty-seventh employee. After thechange, the new application component (not shown) to which the property38 c points now represents the new twenty-seventh employee. But evenwith the change, the property path ‘HRApp.Dept.Employee[26].Salary’still points to the twenty-seventh employee of the indicated departmentand thus the second value 50 c of UI element 46 b displays theappropriate value of the salary of the new twenty-seventh employee,whoever that employee may now be.

The following are additional examples of property paths. For example,the property path ‘App.CurrentSelection.Price’ represents the priceproperty 38 of the currently selected item within a shopping application26. If no item is selected or the current selection changes, then thevalue 50 of this property 38 changes, even though the price property 38of each of the individual items 34 (e.g., objects) within theapplication 26 does not. For another example, the property path‘App.SelectedEmployee.Boss.Boss.Name’ represents the name property 38 ofthe selected employee's boss's boss. This property path will display theappropriate value 50 even if the selection changes (e.g., a differentemployee is selected), if there is a reorganization, or if the bosschanges his/her name. In another example, the property path‘App.Employee[21].Name’ represents the name property 38 of thetwenty-second employee in a table. If the table is sorted or changessize, then this property path will correctly reflect the name property38 of the employee who is, after the revision, currently thetwenty-second employee in the table.

FIG. 2 illustrates an exemplary embodiment of a system 54 that includesa first computing system (“server node”) 60 in communication with asecond computing system (“client node”) 64 over a communication channel94. For example, the communication channel 94 can be over a local-areanetwork (LAN), such as a company Intranet, or a wide area network (WAN)such as the Internet or the World Wide Web. The server node 60 includesa server transceiver 108, the server portion 22 b, a property/eventinterface 90 and the application 26, including one or more applicationcomponents 34. The server node 60 can establish communication over thecommunication channel 94 using a variety of communication protocols(e.g., ICA, HTTP TCP/IP, IPX, SPX, NetBIOS, Ethernet, RS232, and directasynchronous connections). As shown, the server portion 22 b is aseparate process on the server node 60. In other embodiments, the serverportion 22 b, or portions thereof, is located on a server node (notshown) separate from the application program 26. In another embodiment,the property/event interface 90 is included as part of the serverportion 22 b.

The client node 64 includes a client transceiver 104 and an optionalpage interface 112. The page interface 112 includes the client portion22 a and generates (or edits) a page 42, containing dynamic UI elements46. The client node 64 can be any computing device (e.g., a personalcomputer, set top box, phone, handheld device, kiosk, etc) used toprovide a user-interface 42. The client node 64 can be connected to thecommunication channel 94 through a variety of connections includingstandard telephone lines, LAN or WAN links (e.g., T1, T3, 56 kb, X0.25),broadband connections (ISDN, Frame Relay, ATM), and wirelessconnections. As shown, the client portion 22 a is part of the pageinterface 112. The page interface 112 can be, for example, a Web browser(e.g., a MICROSOFT™ INTERNET EXPLORER browser manufactured by MicrosoftCorporation of Redmond, Wash. and/or a NETSCAPE™ NAVIGATOR browser,manufactured by Netscape Communications Corporation of Mountain View,Calif.). In another embodiment, for example, one without a pageinterface 112, the client portion 22 a is a separate process on theclient node 64.

In other embodiments, interaction between the client node 64 and theserver node 60 occurs if the application 26 is executing and the user isinteracting, via the page 42, with the application 26 (i.e., run time).If the user is creating a page 42 (i.e., build time), then there is nointeraction between the client node 64 and the server node 60. Forexample, the user creates a page 42 using the page interface 112 (e.g.,HTML editor, DREAMWEAVER™ software by Macromedia, Inc. of San Francisco,Calif.), as described in more detail with relation to FIG. 4. The userlocates UI elements 46 using the page interface 112. In one embodiment,the user selects a UI element 46 from a set of predefined UI elements 78(FIG. 3). The user associates a property path with the selected UIelement 46. In one embodiment, a property file has the following form:

---start property file-- // List of types used in this property files(identifiers) // String and Number are built in Types: Person Company //Identify the type of the root object RootType: Company // List theproperties. Of the format // <type of object>.<name of property><type ofproperty> // or // <type of object>.<name of property>[] <type ofproperty> // (for indexed properties) // A RW on the end of the lineindicates they property is read/write // // May contain multiple entriesfor a certain object, property pair // if the property can have severaltypes. // Any property may also be undefined Properties: Company.NameString Company.Boss Person Company.Staff[] Person Company.EBW[] PersonCompany.SalaryTotal Number Person.Name String Person.Salary Number RWPerson.ID String Person.Boss Person Person.Staff[] Person // List ofmethods that may be called from the client // in format <objecttype>.<method name>(<argument type...>) Methods: // Hire someone givenname, id, salary, boss App.Hire(String, String, Number, Person) // Firesomeone Person.Fire( ) ---end property file---In another embodiment, the property file has the following form:

-   --- start property file----   RootType: Company-   Company.Name String-   Company.Boss Person-   Company.Staff[] Person-   Company.EBW[] Person-   Company.SalaryTotal Number-   Person.Name String-   Person.Salary Number RW-   Person.ID String-   Person.Boss Person-   Person.Staft[] Person-   App.Hire(String, String, Number, Person)-   Person.Fire( )-   ---end property file---

In one embodiment, the property file containing property paths is storedon the client node 64 for the page interface 112 to access. The propertyfile can contain the types of application components 34 that theapplication 26 creates and the type of properties 38 that each of thetype of application components 34 contain. The property file can alsocontain information regarding the structured relationship betweenapplication components 34 and/or the children application components 34of each type of application component 34. The file can be manuallycreated and/or manually augmented.

In other embodiments, the page interface 112 and/or the client portion22 a has a property browser. In one embodiment, the browser may examinethe code of the application 26 (e.g., JAVA™ compatible classes or sourcecode) and determine possible property paths by examining the type of theget/set property methods. In another embodiment the property browsertemporarily communicates with the server node 60 and initiates executionof the application 26. Upon execution, the property browser can obtainthe instantaneous values of available application components 34, theirproperties 38 and the relationship (e.g., child nodes) between theapplication components 34. After this information is obtained, theexecution of the application 26 and communication between the clientnode 64 and server node are terminated. The property browser can savethe obtained results in the property file.

FIG. 3 depicts the client portion 22 a and the server portion 22 b ofthe property connector API 22 in more detail. The client portion 22 aincludes a protocol module 70 and an event manager 74. In anotherembodiment, the protocol module 70 is located within the clienttransceiver 104 (e.g., FIG. 2). As shown, the client portion 22 b alsoincludes an optional predefined UI elements portion 78, which containsdata to generate specific types of UI elements 46, identified in detailbelow, in connection with FIG. 4. The client portion 22 a communicateswith the UI elements 46 of the page 42.

The server portion 22 b includes a protocol module 82 and a propertypath manager 86. In another embodiment, the protocol module 82 islocated within the server transceiver 108 (e.g., FIG. 2). The serverportion 22 b is in communication with the application components 34 ofthe application 26 through a property/event interface 90. The clientportion 22 a and the server portion 22 b communicate with each otherover the communication channel 94, using a property path protocol asdescribed below. In another embodiment, as shown in FIG. 1, the clientportion 22 a and the server portion 22 b are located on the same machineand are directly connected to each other.

The property connector API 22 associates the user-interface elements 46with the application components 34 using property paths as describedabove. In overview, the functions of the property connector API 22 caninclude:

-   -   (1) collecting and disseminating change events, (a) for the        user-interface elements 46 associated with the properties        38, (b) between the user-interface elements 46 and the server        node 60;    -   (2) communicating change events of particular properties 54        between the client node 64 and the server node 60, and tracking        those change events about which the client node 64 needs to be        informed;    -   (3) dynamically binding property paths to specific application        components 34 (e.g., objects) within the application 26,        reacting to changes in application components 34 along the        property path, and rebuilding the path as appropriate when        instances of application components 34 are created or deleted;        and    -   (4) collecting events from, and communicating property changes        to, individual application components 34.

Anyone one or a combination of any of these functions can be performedby the event manager 74, the property path manager 86, theproperty/event interface 90 and the protocol modules 70 and 82.

During operation of the system 54, the server node 60 executes theapplication 26 and instantiates the application components 34 (e.g.,objects). In one embodiment, for example, the application 26 is writtenin JAVA™ compatible source code, the application components 34 areJAVABEANS™ compatible components and the property/event interface 90includes a JAVABEANS™ compatible API. If not already executing, theserver node 60 also executes the server portion 22 b, which isindependent of the application 26 (i.e., not a part of nor generatedfrom the application 26). The server node 60 executes the server portion22 b in response to the client node 64 requesting execution of theapplication 26 and/or in response to the client node 64 requesting thepage 42 associated with the application 26. If not already executing,the client node 64 executes the client portion 22 a, which isindependent of the application 26 (i.e., not a part of nor generatedfrom the application 26). In one embodiment, for example, the eventmanager 74 of the client portion 22 a is written as a set of JAVASCRIPT™files for a MICROSOFT™ INTERNET EXPLORER browser manufactured byMicrosoft Corporation of Redmond, Wash. and/or a NETSCAPE™ NAVIGATORbrowser, manufactured by Netscape Communications Corporation of MountainView, Calif. The client node 64 executes the client portion 22 a inresponse to a user requesting execution of the application 26 and/or inresponse to the user requesting the page 42 associated with theapplication 26.

The client-side event manager 74 maps the UI elements 46 to theassociated property paths. The event manager 74 maintains a database ofthe mapping of UI elements 46 to property paths. The event manager 74may or may not examine the individual identifiers in the concatenationof a property path. This affects the amount of information that has tobe transmitted between the client portion 22 a and the server portion 22b. In one embodiment, the event manager 74 treats property paths asopaque names. In this embodiment, the event manager 74 does not breakupor examine the individual identifiers in the concatenation of a propertypath, but instead treats the property path as a single, long variablename or as a placeholder. This allows a compression algorithm in theprotocol between the client portion 22 a and the server portion 22 bthat replaces each property path in the page 42 with a single id (e.g.,$1). In this embodiment, there is a dictionary (not shown) on the servernode 60 so the sever portion 22 b can lookup each id and convert the idinto a property path prior to accessing the corresponding property. Inthis Ads embodiment, the server portion 22 b must track all changes toany of the properties corresponding to identifiers in the property pathand determine how those changes affect the value of the one or moreproperty paths including the identifier. The server portion 22 b alsoonly communicates changes to the client portion 22 a in terms ofcomplete property paths.

In another embodiment, the client portion does examine changescorresponding to each individual identifier in the property path and candetermine itself how a change to a property corresponding to a singleidentifier affects one or more property paths including that identifier.In one embodiment, for example, a copy of the property path manager 86is located on the client node 64 and sends all changes (rather than justthe changes in leaf values) in a tree structure 160 (FIG. 6) between theclient portion 22 a and the server portion 22 b. This embodiment addscomplexity to the system 54, but may give bandwidth/performance gains,because the server node 22 b can communicate changes to the clientportion 22 a in terms of individual identifiers. For example, consideran indexed property A with A[0]=X, A[1]=Y and A[2]=Z and each of X, Y,and Z application components 34 with three properties 38 a, b, and c. Ifthe table is resorted so that A[0]=Y A[1]=Z and A[2]=X, in the system 54(FIG. 3), nine property change events are sent from server portion 22 bto the client portion 22 a (i.e., one each for the properties A[0].a,A[0].b, A[0].c, A[1].a, A[1].b, A[1].c, A[2].a, A[2].b, and A[2].c). Inthe copy of the property path manager 86 is located on the client node64, the server portion 22 b sends three property change events (i.e.,A[0], A[1] and A[2]), to the client portion 22 a because the copy of theproperty path manager 86 on the client node 64 has all of the childrennode information and can make the applicable changes.

As depicted in FIG. 3, the event manager 74 sends to the server-sideproperty path manager 86 all of those property paths in which the eventmanager 74 has interest. The event manager 74 registers interest in aproperty path using, for example, a ‘ListenTo’ command shown in Table 1.When the event manager 74 informs the server portion 22 b about whichproperty paths are of interest, the event manager 74 does not need toinform the server portion 22 b specifically which (or how many) UIelements 46 are interested in each property path. The property pathmanager 86 monitors the properties 38 of the application components 34corresponding to the identified property paths and notifies the eventmanager 74 when any of the property paths in which the client portion 22b has registered interest in changes. When the user provides some input,by interacting with one of the user-interface elements 46, the eventmanager 74 notifies the property path manager 86 about the change and towhich property path the change corresponds. Because the communicationreferences property paths, the communication about the change is interms of the effect on the application components 34, rather than interms of the user-interface elements 46. For example, if the user slidesa horizontal slider to the 50% point, the UI element determines thevalue the 50% point represents and signals an event to the event manager74.

When a property path is no longer of interest, the event manager 74 cansend a notice of lack of interest to the server portion 22 b in one ofseveral different ways. For example, the event manager 74 canimmediately inform the server portion 22 b, not inform the serverportion 22 at all, or inform the server portion 22 b after some timeperiod or other event (e.g., when first notified about a change in thecorresponding property of the property path). The server portion 22 btransmits to the client portion 22 a any change events associated withthose property paths in which the client portion 22 a has indicatedinterest. When the event manager 74 receives a property change event fora change in the state (e.g., value) of a property 38 associated with aproperty path from the server portion 22 b, the event manager 74determines, using the mapping, which UI elements 46 must be notified.The event manager 74 communicates the updates due to the change event toeach of the UI elements 46 mapped to the property path. In oneembodiment, there are multiple pages 42 located in separate sub-windows.The event manager 74 is configured to inform UI elements 46 that arelocated in other sub-windows about any applicable changes. In thisembodiment, the event manager 74 manages the database of the mapping sothat the closure of a window does not adversely affect the other UIelements 46. In this embodiment, the event manager 74 and/or associateddata structures may be replicated or distributed between the differentpages. For example, each page may contain a portion of the event manager74, and a table of UI elements 46 that are present on that page.

If the user updates a UI element 46, the UI element 46 signals a changeevent to the event manager 74 and is updated on the display as the usermakes a change. When the event manager 74 receives a change event fromthe UI element 46, the event manager 74 determines, using the mapping,which other UI elements 46 are mapped to the same property path as theUI element 46 that changed. The event manager 74 communicates theupdates due to the change event to each of the other UI elements 46mapped to the same property path. The event manager 74 also sends achange event to the server portion 22 b so that the server portion 22 bcan update the associated property 38 of the application component 34 inresponse to the user change of the UI element 46.

In another embodiment, the event manager 74 does not make any immediatechanges to the UI element 46 that the user changes or any other UIelements 46 mapped to the same property path. Instead, the event manager74 first sends a change event to the server portion 22 b so that theserver portion 22 b can update the associated property 38 of theapplication component 34 in response to the user change of the UIelement 46. The application 26 can reject the change initiated by theuser for security or other reasons. The event manager 74 waits until theserver portion 22 b sends back a change event indicating that theproperty 38 of the application component 34 associated with the propertypath has changed. After the event manager receives that change eventfrom the server portion 22 b, then the event manager 74 communicates theupdates due to the change event to each of the other UI elements 46mapped to the same property path. If the application rejects the change,then the event manager 74 updates the UI element 46 that the userchanged back to its pre-user intervention state.

In some embodiments, the property connector API 22 takes steps to avoidlooping of change events, which can result in trying to update a UIelement 46 or an application component 34 that generated the changeevent and has already been updated. For example a UI element 46 onlygenerates a change event if a user updates the UI element 46 , forexample, but does not generate a change event if the event manager 74updates the UI element 46. In another embodiment, for example, theproperty connector API 22 does not inform the original generator (i.e.,UI element 46, application component 34) of the change event, as thatoriginator is already updated.

A page 42 can also be altered dynamically when, for example, an iteratortype predefined UI element 78 creates additional UI elements for indexedproperties, a process described in more detail below. If a page 42 isbeing altered dynamically, then when a UI element 46 is generated, theevent manager 76 determines those property paths in which the UI element46 is interested. Similarly, when a UI element 46 is destroyed, theevent manager 74 determines that the UI element 46 is no longerinterested in those property paths. In one embodiment, the user haspreviously created the page 42 separately (i.e., at build time) and thussome or all of the UI elements 46 on the page 42 are created prior tothe application 26 executing. In an embodiment using treeview type oriterator type predefined UI elements 78, an example of a portion of theUI (e.g., a row in the table) is included in the page 42 at build time.At runtime, the client portion 22 a duplicates/clones the example (e.g.,row) for all of the members of the indexed property associated with thetreeview type or iterator type predefined UI element 78, as described inmore detail below. The example portion of the UI may be a single UIelement or a more complex set of UI elements.

FIG. 4 depicts an embodiment of a screenshot 128 produced by the pageinterface 112 (FIG. 2) (e.g., an HTML editor) that helps a user generatea UI 42′ at build time according to the invention. The screenshot 128includes a display 130 of an HTML page 42′ that a user is generatingwith the page interface 112. The screenshot also includes a palette 134of some available predefined UI elements 78 (FIG. 2) and an entrydisplay 138 for assigning a property path to a UI element 46′.

The palette 134 of available predefined UI elements 78 includespredefined UI elements 78 a, 78 b, 78 c, 78 d, 78 e, 78 f and 78 g.Predefined UI element 78 a represents an image type UI element. Theimage type predefined UI element 78 b displays an image dependent on thevalue of the associated property (e.g., ‘property-value’.gif).Predefined UI element 78 b represents an iterator type UI element. Aniterator type repeats a UI element for each member of a range of indexedproperties (e.g., once each for i=0, i+1, i=2, . . . in App.Staff[i]).The element 46 g′ represents an iterator type element, where the row 46g′ is an exemplary row that the client portion 22 a copies whendynamically creating elements for each index value.

Predefined UI element 78 c represents a text type UI element. The texttype predefined UI element 78 c displays a property value as a piece oftext. The elements 46 b′, 46 c′ and 46 d′represent text type elements.With a text type predefined UI element 78 c, numeric values may bescaled, stepped and/or clipped. Predefined UI element 78 d represents ahidden type UI element. A hidden type hides and shows part of the UIelement, dependent on a property and an expression. Predefined UIelement 78 e represents a value type UI element. The value typepredefined UI element 78 e is an input box that displays a propertyvalue and allows it to be edited by a user. The element 46 e′ representsa value type element. Predefined UI element 78 f represents a slidertype UI element. The slider type predefined UI element 78 f includes avertical slider and/or a horizontal slider for numeric properties. Theelement 46 f′ represents a slider type element. When the user selectsthe slider type UI element, the user also enters values associated with‘min’ ‘max’ and ‘step’ values for that slider element. In anotherembodiment, the user enters the property paths for the values associatedwith ‘min’ ‘max’ and ‘step’ values for that slider element and theproperties corresponding to those property paths determine theassociated values. Predefined UI element 78 g represents a treeview typeUI element. The element 46 a′ represents a treeview type element. Thetreeview type predefined UI element 78 g is based on the levels of aproperty path. For example, for the property path‘App.Boss.Staff[i].Staff[j]’ the treeview has a root level, a childlevel and a child's child level. The root level is App.Boss, the childlevel is App.Boss.Staff[i], and the child's child level isApp.Boss.Staff[i].Staff[j].

In other embodiments, the palette 134 can include other predefined UIelements 78. For example, a button type disables a button based on aproperty value associated with a property path. An iframe type displaysan embedded frame, where the contents of the frame are constructed froma page described by the value of property path. An anchor type createsan anchor which links to a page described by the value of a propertypath. The tab type predefined UI element displays associated propertiesas tabs, with one tab per member of a range of indexed properties. Aflipflop type changes the style of part of a UI, dependent on a propertyand an expression. For example the flipflop will set the style of thepart of the UI to one state (the flip state) if the expression evaluatesto ‘false’ when a placeholder in the expression is substituted by thecurrent value of the property. If the expression evaluates to ‘true’then the style of the part of the UI is set to an alternative state (theflop state).

A deck type displays one of a ‘deck’ of portions of a UI, dependent on aproperty value (each UI portion is associated with a value, an the onewhose value matches the current value of the property is displayed). Adropdown type is a nested dropdown menu, where each choice is a valuefrom a range of indexed properties. A radio type has one or more radiobuttons, where each has a property path and an associated value to setthe property path to if the button is selected. All UI elements maycontain an expression in terms of a number of property paths, ratherthan a simple property path. For example, the expressionApp.Employee[0].Salary+App.Employee[1].Salary would use the sum of thevalue of these two properties to update the UI element, rather than anindividual property value. A script type element executes a script onthe client node 64 whenever a value of a specified property changes, andpasses the value of the property as an argument to the script.

To create the HTML page 42′, the user selects a UI element 46′ generatedby the page interface 112 and places the selected UI element 46′ at thedesired location in the page 42′. The user can also select from thepredefined UI elements 78 shown in the palette 134. The user selects apredefined UI element 78 and places the selected predefined UI element78 at the desired location in the page 42′. This placement can be done,for example by the click and drag method. Alternatively, the user canmove the cursor to the desired insertion point, and then click on theitem from the palette 134. The client portion 22 a generates a dialogbox that prompts the user to enter relevant attributes (e.g., propertypath, min/max values, etc). When the user enters all of the relevantattributes, the client portion 22 a locates the selected element 78 atthe cursor position.

The user uses the entry display 138 to edit a property path associatedwith a UI element 46′ selected in the page 42′. To make the association,the user can type in the property path. In another embodiment, to makethe association, the user can search through a list (e.g., structuredtree) of available property paths for the application 26 and select aproperty path from the list. As described above, in one embodiment thelist is provided through a property file containing identifiers andtheir relationships, and the page interface 112 accesses the propertyfile, which is stored on the client node 64. In other embodiments, thepage interface 112 and/or the client portion 22 a includes a propertybrowser. The property browser obtains the instantaneous values ofavailable application components 34, their properties 38 (e.g.,identifiers) and the relationship (e.g., child nodes) between theapplication components 34 and properties 38 to provide a list ofavailable property paths. In another embodiment the property browserexamines the code of the application and determines possible propertypaths by examining the types of the application objects.

Once a user locates all desired UI elements 46′ in the page 42′ andassociates them with property paths, the page 42′ is ready to be usedwith the application 26. FIG. 5 depicts a screenshot 150 of a page 42″being used in conjunction with an executing application (i.e., runtime). The page 42″ contains a treeview type UI element 46 a″ thatdisplays the structured relationship between the employees. The page 42″also contains a large number of text type UI elements. Text type UIelements 46 b″, 46 c″ and 46 d″ that display the text values ofproperties that correspond to the ‘selected’ employee. This currentselection is also reflected in (and may be changed using) the tab typeUI element 46 g″. Image type UI element 46 h″ displays an image thatcorresponds to the selected employee . The value type UI element 46 e″(i.e., input box) and the slider type UI element 46 f″ display thesalary that corresponds to the selected employee. The user can use anyof the UI elements associated with the ‘salary’ property path (e.g., 46e″, 46 f′) to change the salary that corresponds to the selectedemployee. As discussed above, when a user changes any one of these UIelements 46 e″, 46 f′, the client portion 22 a changes all of the otherUI elements 46″ with the same property path so that they all stayconsistent. This change to the UI elements 46″ is done entirely on theclient node 64 without any interaction from the server node 60. Theclient portion 22 a also notifies the server portion 22 b of the change,so the server portion 22 b can update the appropriate property 38.However, the application 26 may veto the change either by not providinga ‘set’ method for the property 38, or by rejecting the call via vetomeans available in the property/event interface 90 (e.g., for JAVABEANS™compatible components, this veto might be in the form of a “throw”statement using an “exception” sub-class). If the change is vetoed, theproperty path manager 86 informs the client portion 22 a that the valuehas changed back to its old value, so that the correct value isdisplayed on the client node 64.

Other text type elements on the page 42″ include 46 j″–46 n″, which areall dynamically created by copying an example treeview entry 46 a′ (FIG.4) and substituting in the appropriate property path for the position inthe treeview (e.g., App.Boss.Name, App.Boss.Staff[0].Name,App.Boss.Statf[0].Staff[0] Name, App.Boss.Staff[0 ] .Staff[1] .Name,App.Boss.Staff[1] Name respectively). The client portion 22 a similarlycreates text elements 46 o″–46 t″ in the table 46 i″ from an exemplaryrow of the table (e.g., 46 g′ of FIG. 4) and by substituting the indexvalues 0, 1, 2, 3, and 4 into the indexed property path‘App.Employee[*]Name’.

FIG. 6 depicts a block diagram of an embodiment of a map of registeredproperty paths generated by the property path manager 86. The propertypath manager 86 generates this map to track all of the property paths inwhich the client portion 22 a registers interest and the properties 38of the application components 34 to which the property paths correspond.In the embodiment shown, the map of the property path manager 86 ismodeled as a tree structure 160. The tree structure 160 is associatedwith an application 26′ including application components 34 a′, 34 b′,34 c′, 34 d′ (generally 34′), some of which include properties 38 a′, 38b′ 38 c′ (generally 38′). The tree nodes 164 a, 164 b, 164 c, 164 d(generally 164) of the tree 160 are associated with the root component34 a′ and existing properties 38 of application components 34′ withinthe application 26′ if the appropriate application component 34′currently exists. If the property path does not currently refer to avalid application component 34′, then the tree node 164 is notassociated with any application component 34′. In another embodiment,the property path manager 86 generates a tree 160 representing all ofthe available property paths currently available for a specificapplication (not shown). In this embodiment, the property path manager86 transmits all of the available property paths to the client portion22 a for use in generating a page 42″, as mentioned with respect to FIG.4.

As shown, the client portion 22 a has registered interests in propertypaths ‘App.X.Y’ and ‘App.X.Z’, represented by tree nodes 164 c and 164d, respectively. X, Y and Z represent properties of the applicationcomponents 34′ and these properties correspond to the identifiers of theproperty paths. For further illustration, property path ‘App.X.Y’ canrepresent the property path ‘App.Employee[3].Name’ and ‘App.X.Z’ canrepresent the property path ‘App.Employee[3].Boss’. The initial valuethat corresponds to the property path ‘App.Employee[3].Name’ isrepresented by property 38 a′, or the value ‘Alf’. The applicationcomponent that corresponds to the property path ‘App.Employee[3].Boss’is represented by application component 34 d ′ and the name property ofthat application component is 38 c′, or ‘Chris’.

When the state of the application component 34′ changes, theproperty/event interface 90 notifies the property path manager 86. Theproperty path manager 86 updates the corresponding tree node(s) 164 inthe property path tree 160. If the updated tree node(s) 164 represents acomplete property path in which the client portion 22 a has registeredinterest, the property path manager 86 sends, or queues for sending, achange event to the client portion 22 a. The property path manager 86subsequently recursively examines each of the tree node's childrennodes. In this examination, the property path manger 86, via theproperty/event interface 90, obtains a new value of a property 38′ fromthe application 26′, and if another value of a registered propertychanges, transmits a change event to the client portion 22 a. Theresults are that the change in the state of one property can result inmany property change events being notified to the client portion 22 a.The property path manager 86 terminates the recursive examination whensomething is found to be unchanged. For example, any child node of treenode 164 d is not examined, as the value of the tree node 164 d isunchanged.

In the embodiment shown in FIG. 6, the value of property path ‘App.X’changes from application component 34 b′ to 34 c′. In the‘App.Employee[3]’ property path example, this change represents a changein the third employee. The client portion 22 a is not interested in the‘App.X’ property path, so the property path manager 86 does not generatea change event for this change. However, the client portion 22 aregistered interest in the property path ‘App.X.Y’, and the value of theproperty corresponding to that property path has now changed from 38 a′,‘Alf’, to 38 b′, ‘Betty’. The property path manager 86 determines thischange when it recursively examines the children tree nodes Y 164 c andZ 164 d of tree node X 164 b. Significantly, this recursive examining iswhat allows the property connector API 22 to maintain the looselycoupled connection between UI elements 46 and application components34′.

For example, consider when the application 26′ is not configured togenerate a change event when the name of the third employee has changed,the value represented by the property path ‘App.Employee[3].Name’, butthat the application 26′ is configured to generate a change event whenapplication components 34′ are generated and/or deleted and whenproperties 38′ of existing application components 34′ change. Theproperty path manager 86 converts those change events that theapplication 26′ can generate into change events associated with propertypaths in which the client portion 22 a has interest by examining itstree structure 160. Referring back to the change from applicationcomponent 34 b′ to 34 c′, both of these application components 34 b′, 34c′ point to application component 34 d ′. The client portion 22 a hasregistered in the property path ‘App.X.Z’ and this value remainsunchanged, despite that fact that App.X now refers to a differentapplication component 34 c′. In the ‘App.Employee[3].Boss’ property pathexample, this represents that the boss of the new third employee,represented by application component 34 c′, is still the applicationcomponent represented by 34 d′. Because there is no change associatedwith the registered property path ‘App.X.Z’, the property path manager86 does not generate a change event.

Because the property path manager 86 converts changes to states of aproperties within an application 26′ to change events associated withproperty paths, the client portion 22 a can register interest in specialtype property paths. One special type is a cross-mapped property path.The cross-mapped property path is in the form, for example, Map(“v#r”).The cross-mapped special type represents a relationship between a value“v”, specified with a property path, and a range of possible values “r”,specified with a wildcard property path. The value of the cross-mappedproperty path is the property path within the range “r” that has thesame value as “v”. For example, if “v” is “Session.CurrentEmployee”, “r”is “App.Employee[*]”, and the currently selected employee is the 3^(rd)entry within the App.Employee enumeration then the value ofMap(“Session.CurrentEmployee#App.Employee[*]”) is 2.

Described another way, cross-mapping is a lookup of one property path,dependent on information from a second property path. For example, whenthe property path manager 86 receives the commandMap(“Session.Current#App.Employee[*]”), the property path manager 86examines the first property path “Session.Current” and determines thevalue v of the property path. The property path manager 86 then looks upthe value v within the second property path, where the value v replacesa wildcard identifier of the second property path. The value of thecross-mapping is the index that matches. For example if the state of thefirst property path “Session.Current” is ‘Barbara’ and the correspondingstates of the second indexed property paths are:

-   -   App.Employee[0] is Abe    -   App.Employee[1] is Barbara    -   App.Employee[2] is Charlie    -   App.Employee[3] is Diane,        then the value of the cross-mapping        “Session.Current#App.Employee[*]” is equal to 1

The second property path may contain several wildcards identifiers, andthe value will be the ‘route’ through all of these wildcard identifiers.For example, for the cross mapping is“Session.Current#App.Boss.Staff[*].Staff[*]”. The state mapped to thefirst property path is “Session.Current”=Ben. The corresponding statesof the second indexed property are:

-   -   App.Boss.Staff[0].Staff[0]=Alice    -   App.Boss.Staff[0].Staff[1]=Ben    -   App.Boss.Staff[1].Staff[0]=Chelsea.

The value of the cross-mapping of“Session.Current#App.Boss.Staff[*].Staff[*]” is equal to 0,1.

Another special type is an indexed property path. In the JAVABEAN™compatible API, and other similar APIs, there is a concept of ‘indexed’properties. The indexed property A acts like a number of properties‘A.size, A.0 A.1, A.2 . . . A.(size-1)’. The property connector API 22follows this indexing by representing such properties in property paths‘A[], A[0], A[1],A[2] . . . A[size-1]’, respectively. The iterator typepredefined UI element 78 (FIG. 3) uses the special type indexed propertypath.

The iterator type predefined UI element 78 includes a template and islinked to an indexed property path. The template represents the layoutof the iterator type predefined UI element 78 for a single member (i.e.,a single index value) of the property path. During execution, theiterator type predefined UI element 78 creates a copy of the templatefor each member of the indexed property, and modifies the copy so thatit is associated with a property path with the corresponding indexvalue. These new copies are inserted into the user interface asadditional UI elements 78. If the range of the indexed propertyincreases (or decreases), more copies are inserted (or removed) asrequired, so that there is one UI element 78 for each currentlyavailable index value. Each copy is linked to the application via itsassociated property path. An identical approach is taken for treeviews,and rows of drop-down menus.

For example, the ‘iterator’ UI element 78 provides a table with a‘template’ row. The ‘iterator’ UI element 78 duplicates this ‘template’row for each member of the indexed property. Each row can containarbitrary UT elements 46 with ‘wildcard’ pathnames (i.e., propertypaths) that have the current row number substituted in prior toregistration. This is shown in the following exemplary code:

<table> <tbody style=‘display:none’ widget=‘iterator’range=‘App.Employee[]’> <tr> <td> <span widget=‘text’variable=‘App.Employee[%idx].Name’>Name</span> <td> <td> <spanwidget=‘text’ variable=‘App.Employee[%idx].Salary’>Salary</span> <td></tr> </tbody> </table>There are a number of other UT elements (e.g., tab, menu, list) thatalso iterate over indexed properties and share the iterator optimizationof being able to display a plurality of elements associated with indexedproperty paths using a single exemplary element, as described above.

Referring back to FIG. 3, the property/event interface 90 transmits data(e.g., change events, value changes) between the property path manager86 and the application 26. This interface 90 uses an appropriate API forthe implementation of the application 26. In one embodiment, forexample, the application 26 is JAVA™ technology-based, and the standard‘JAVABEAN™ Property API’ provides the required semantics and is thusused as the property/event interface 90. This standard API 90 allows theproperty path manager 86 to change the values of properties 38 ofapplication components 34 when those values have been changed by a userthrough a UI element 46. This standard API 90 also notifies the propertypath manager 86 about changes within the application 26. Otherembodiments can include COM objects 34 and a COM property change API 90and/or C++ objects 34 with associated API 90.

The client portion 22 a and the server portion 22 b communicate witheach other over the communication channel 94. The protocol modules 70and 82 establish low-level communication by use of a communicationslayer. An exemplary protocol is described in Table 1. The protocol canvary from Table 1 depending on how the client portion 22 a and the severportion 22 b are divided between the client node 64 and the server node60 (e.g., copy of property manager 86 on the client node 64, serverportion 22 b and client portion 22 a directly connected to each other onsame node, etc.). In another embodiment, the protocol modules 70 and 82are part of the client transceiver 104 (FIG. 2) and the servertransceiver 108 (FIG. 2), respectively.

During communication, the server node 60 and the client node 64 batchthe communication into a number of messages, which may be compressed orencrypted. For example, in one embodiment, the server node 60 and theclient node 64 use HTTP as the transport protocol. The client node 64sends the server node 60 one or more messages. The server node 60processes the one or more messages, which may result in various propertychange events. The server node 60 batches all of the messages queued tobe sent to the client node 64 and sends them as the response to the HTTPrequest from the client node 64. In one embodiment, batching involvesthe removal of ‘outdated’ changes. For example if a change list in thebatch of queued messages includes A.B.C=x . . . A.B.C=y, the entry‘A.B.C=x’ is overwritten by the subsequent entry ‘A.B.C=y’ and can besafely discarded. In one embodiment, the batching process also sorts theentries lexicographically in order to aid compression.

The communications protocol, as illustrated in Table 1, relies oninforming the client node 64 about which property paths within theapplication 26 have changed. Communicating in terms of changes to valuesof property paths is typically a lower overhead than informing theclient node 64 about which of the client's display elements 46 toupdate, and how to update them. In the system 54, the role of the clientnode 64 is to reflect the current state of the application 26. Ifnetwork or communication channel latency is high, then the client node64 displays an incomplete state, but the application 26 can continuefunctioning correctly. The application 26 continues because the clientnode 64 and the server node 60 are more loosely coupled than intraditional systems. The server node 60 can be completely unaware of thetype of client, or the way in which the client node 64 chooses toreflect the changes in the state of the application 26. This makes theserver node 60 more stable and scalable, as new client node 64 featuresdo not affect the server node 60 or the execution of the application 26.

TABLE 1 Direction Message Meaning C −> S Start Inform the server that aclient wishes to start a (identifier new application or reconnect to arunning one. for One client may simultaneously run several applicationapplications. The server may veto the execution instance, of anapplication, based on a stored security application policy descriptor) C−> S ListenTo Register interest in an application property. (applicationThe server should immediately generate a identifier, property-changeevent for the property to tell pathname) the client the current value. C−> S Map Register interest in a cross-mapped property. (applicationCross-mapped properties are described above. identifier, map identifier,pathname 1, pathname 2) C −> S Drop Remove interest in specifiedproperty. (application identifier, pathname) C −> S Set Set thespecified property to the specified (application value. identifier,pathname, value) S −> C Application Inform the client that the value ofa property identifier, has changed. Pathname = value C −> S Invoke Tellthe server to parse and execute the (Application specified string. Thismust represent a call to identifier, an accessible method on an objectwithin an string) application (specified by pathname). Any return valuefrom the call is discarded. The call is represented by a string of thefollowing form Pathname.MethodName (arg, arg, arg . . . ) where arg iseither a constant (a number or string) or a property path. The servermay veto the execution of such methods based on a stored securitypolicy. C −> S Null Used as a heartbeat to indicate to the server thatthe client is still in existence. C −> S Close End the application.(application identifier) Notes: S = server node 60, C = client node 64,pathname = property path.

In other embodiments, the protocol modules 70 and 82 are configured toemploy compression schemes within the communications layer that theyestablish. A property path compression scheme is used within a batch ofmessages sent within the client node 64, within the server node 60and/or between the server node 60 and the client node 64. Whenever abatch of messages is sent, the property names used in the second andsubsequent message is compressed by sending only the difference betweenthe required property name and the previous property name. For example,rather than sending the message C->S‘ListenTo(“Session.Current.Name”),ListenTo(“Session.Current.Salary”)’,the client node 64 sends the message ‘C->SListenTo(“Session.Current.Name”),ListenTo(16+“Salary”)’, where 16 is thenumber of characters of “Session.Current.Name” that also occur in“Session.Current.Salary”. The client node 64 takes advantage of thepreceding message by shortening the subsequent message.

Another scheme to shorten the length of messages is for the client node64 to register interest in a number of property paths by using a wildcard. For example, this scheme is used to register interest in all theproperty paths that supply values for a table. To illustrate thisexample, the single message ‘C->S ListenTo(“App.Employee[*].Name”)’registers interest in the property paths ‘App.Employee[0] .Name’,‘App.Employee[1].Name’ . . . ‘App.Employee[n−1]Name’, where n is thesize of the App.Employee indexed property. In addition, if the size ofthe App.Employee property changes, then the client node 64 hasimplicitly registered interest in all App.Employee[0 to m−1].Namevalues, where m is the new size.

The property connector API 22 also compresses the property path names.From the server portion 22 b to the client portion 22 a, in response toa wildcard Listen To request (as in the example above) the serverportion 22 b compresses its responses by omitting property path names.Rather than sending the messages:

-   -   S->C App.Employee[0].Name=Alf    -   S->C App.Employee[1].Name=Bert    -   S->C App.Employee[2].Name=Carl,        the server portion 22 b sends    -   S->C array=App.Employee[*].Name    -   S->C arrayelement=Alf    -   S->C arrayelement=Bert    -   S->C arrayelement=Carl,        where array and arrayelement are special property names that may        be sent efficiently.

The system 54 uses a data compression scheme in messages sent from theserver node 60 to the client node 64. The client node 64 stores, at alltimes, the ‘last known’ value 50 of each of the property paths that itis displaying in the page 42 in a current value table. In oneembodiment, the server node 60 optionally stores a copy of thisinformation, and uses this as a data dictionary to compress values sent.For example, the server node 60 needs to transmit to the client node 64the message S->C App.Employee[4].Name=“Albert”. The server node 60determines, by examining the data dictionary, that the client node 64already has the value App.Employee[3].Name=“Albert” by a previoustransmission, and upon determining the value that was sent, then theserver node 60 compresses its message to S->CApp.Employee[4].Name=copyValue(App.Employee[3].Name), where copyValue isa directive to the client node 64 to use a value 50 from its currentvalue table.

In another embodiment, the protocol modules 70 and 82 are configured toemploy the data compression scheme in parallel with the property pathcompression scheme and an array name compression scheme. The protocolmodules 70 and 82 utilize this combination of schemes when the size ofthe description of the ‘copyValue’ expression is smaller than theliteral value. The array name compression scheme is of particularbenefit when an array of data on the server node 60 is sorted, and thisdata is displayed in the UI 42 on the client node 64. The combination ofcompression schemes described above compresses the message

-   -   S->C App.Employee[0].Name=“Albert”        -   App.Employee[1].Name=“Bert”        -   App.Employee[2].Name=“Cathy”        -   App.Employee[3].Name=“Doug”        -   App.Employee[4].Name=“Elsie”            to    -   S->C array=“App.Employee[*].Name”        -   arrayelement=copyValue 4        -   arrayelement=copyValue 3        -   arrayelement=copyValue 2        -   arrayelement=copyValue 1        -   arrayelement=copyValue 0.

In other embodiments, the property connector API 22 is configured sothat the server node 60 resource utilization is low. Generally, thereare no ‘per-client’ threads and little ‘per-client’ state and backgroundprocessing. There are three classes of applications 26 that can beoptimized for scalability, by reducing the amount of processing orstorage done per client, or per change. The first class of applications26 that can be optimized are responsive to user input, but do notpro-actively change values of properties 38. If the client node 64 isdormant, the property connector API 22 can optimize the resource usageon the server node 60 by suspending the application 26 and/or storingclient-specific state on the client node 64 until the client node 64becomes active again.

The second class of applications 26 that can be optimized are those thatact as data feeds, for example stock prices. With this class ofapplications 26, the per-client data is small, whereas the shared datamay be large. The property connector API 22 again stores client-specificstate on the client node 64 rather than the server node 60 , allowingthe server node 60 to scale to more client nodes 64. For this class ofapplications 26, the property connector API 22 allows a single ‘workerapplication instance’ to service many clients 64.

The third class of applications 26 that can be optimized are those thatgenerate events faster than the client node 64 can collect them. Anexample is a stock ticker application that sets the price of a stockevery second and communicates with a client node 64 that reads the stockprice once every minute. The property connector API 22 reduces the rateof event generation, without involvement from the application 26, toreduce the per-event processing load. This is particularly important forthe third class of applications with a large number of clients 64. Forapplications where the rate of event generation is high compared to therate of polling by clients, there is a higher than necessary per-clientevent processing load for connected clients. In one embodiment, theproperty connector API 22 adds event buffering mechanisms so that theper-event cost is much lower. For example, only one record is updated onthe server per event, rather than one per client. At a lower period ofevent generation, the property connector API 22 scans these records andforwards events to the client records. The property connector API 22matches, in effect, the rate of event generation to the rate of polling.

For these three classes of applications 26, the property connector API22 supports different modes of operation where the per-client stateand/or processing on the server node 60 is further reduced. This is atthe expense of increased bandwidth and/or processing requirements whencommunication does take place, or at the expense of reduced timelinessof event notification. A client connection may move from a ‘highlyinteractive’ mode of operation to a ‘resource saving’ mode of operationand back many times during its lifetime. Equally, the rate of eventgeneration may be varied according to the server load.

In one embodiment, there are two operating modes for property connectorAPI 22, and additional operations within the operating modes. The normalmode of operation, described above, is called connected mode. The server60 stores, for each client 64, an instance of the application 26 and aproperty graph of listener objects 34. In connected mode, there is highper-client state stored on the server 60 and high per client eventprocessing load. However this is low per client poll/invocationprocessing load, and thus low bandwidth is required.

The second mode of operation is disconnected mode. In disconnected mode,the client state is removed from the server 60 and stored on the client64. No per client event processing takes place. Either no application 26is running on the server 60, or only a single shared instance isexecuting. However, sufficient state is stored on the client 64 to allowthe per-client application 26 to be recreated when necessary. The client64 also stores a description of each property it is interested in, as inconnected mode. The property connector API 22 allows a client 64 indisconnected mode to poll. This poll has higher processing and bandwidthcosts associated with it than in connected mode. A disconnected client64 wishing to perform an invoke command (Table 1) must reconnect. Movingfrom disconnected mode to connected mode, and back, incurs relativelyhigh bandwidth and processing overhead.

The additional operations are specific optimization techniques for finetuning the connected and disconnected modes of operation for deploymentswith a large client population. The additional operations aredisconnect, reconnect, and one-shot. For the disconnect operation,issued by client 64, the property connector API 22 commands theapplication 26 to save its state and shut down. This saved state is thensent to the client 64. No per-client state remains on the server 60. Theconnection then enters the disconnected mode. Heuristics determine whento enter the disconnected state. Entering the disconnected state is onlypossible for applications 26 that provide a suitable interface, or wherea saved state can be created by logging the history of all operationsinvoked.

During the reconnect operation, issued by client 64, the client 64 sendsthe saved application state to the server 60 along with a list ofproperties 38 that the client 64 is interested in. The server 60restarts the application 26 using the saved state, re-registers interestin all properties 38, and continues in the connected mode. Thisoperation is invoked by a disconnected client 64 that wishes to updatethe server state (i.e., invoke an operation or set a property).

During the one-shot operation, issued by client 64, the client 64 sendsthe saved application state to the server 60 along with the list ofproperties 38 that the client is interested in. The server 60 mayrestart the application 26, return the current values of the properties38 and then shut down the application 26. For an application 26 to usethis optimization, it must provide the required static method, forexample, a single shared instance, or static method, that can take asaved state and return a suitable application instance. This suitableinstance may be a shared instance between several clients or may be anew per-client instance. After the property connector API 22 obtains theproperty values, the property connector API 22 commands the application26 to stop execution. The one-shot operation is invoked by adisconnected client 64 that wishes to poll, but not change the serverstate.

In other embodiments, the property connector API 22 is furtherconfigured with additional optimizations such as timestamp, slow garbagecollector, connectivity check and property set. One optimization thatthe property connector API 22 uses is the timestamp. For manyapplications based on data feeds (e.g. stock tickers), the majority ofproperties 38 that a client 64 has registered interest in may not changebetween polls. In the disconnected mode, this may result in one-shotoperations providing a large amount of unnecessary state data. Toalleviate this, the property connector API 22 adds a timestamp-basedproperty interface. For example, in one embodiment, the propertyconnector API 22 uses the two commands ‘Timeid getCurrentTimestamp( )’and ‘Object getChangedProperty(String name, Timeid since)’. The‘getChangedProperty’ command returns a property value if it has changedsince the specified timestamp. The ‘getCurrentTimestamp’ command returnsthe current time. In replies from disconnect or one-shot operations, theserver 60 provides the current timestamp as an additional parameter. Incalls to one-shot or reconnect operations, the client 64 provides thistimestamp, and is informed of property values if they have changed sincethis timestamp was issued.

In another embodiment, the property connector API 22 uses the slowgarbage collector optimization, which requires the cooperation of theapplication 26. When a client 64 performs a reconnect and/or one-shotoperation, if the previous application instance is still available(i.e., has not been garbage collected), then this instance can be usedas in connected mode. This optimization does not apply if theapplication 26 has been ‘stopped’ explicitly on disconnect, but manyapplications are ‘passive’ and do not require a stop interface.

In another embodiment, the property connector API 22 uses theConnectivity Check collector optimization. When using the ‘slow garbagecollector’ optimization, above, a client 64 wishing to perform reconnector one-shot operations first determines whether the server 60 still hasa valid application instance. If the server 60 does, then the savedstate and property list does not need to be sent. When successful, thisoptimization reduces the bandwidth requirement. When unsuccessful, itincurs an additional ‘round trip’ from the client 64 to the server 60and back.

In another embodiment, the property connector API 22 uses the propertyset optimization. It is noted that if a server 60 is supporting a largenumber of clients 64, all of which use the same user-interface, then itis likely that many of the clients 64 will be interested in exactly thesame set of properties. During disconnect mode, the server 60 associatesthe set of properties 38 that the client 64 is interested in with an setidentifier, and the client 64 uses this set identifier during one-shotand reconnect operations, rather than sending the complete list ofproperties 38. Using the set identifier incurs a small additional memoryrequirement on the server 60, as many clients share the same propertyset, but saves considerably in the bandwidth requirement of the one-shotand reconnect operations.

FIG. 7 depicts a flow diagram of an embodiment of a process by which theserver node 60 and client node 64 interact in accordance with theinvention. The first step is that the client node 64 establishes aconnection with the server node 60 to connect (step 200) to an executingapplication 26 or to request (step 200) initiation of execution of theapplication 26. The server node 60 authenticates the client node ifrequired and connects the client node 64 to the application 26, ifexecuting, or initiates execution of the application 26 as requested(step 204).

The client portion 22 a scans the UI 42 and identifies (step 208) a UIelement 46 within the UI 42 that is associated with a property path andhas not been initialized (e.g., inserted into table and registered). Theclient portion 22 a inserts (step 212) into its table the identified UIelement 46 and its associated property path. The client portion 22 aregisters (step 216) interest in this property path with the serverportion 22 b. The client portion 22 a determines (step 220) whetherthere are any more UI elements 46 in the UI 42 that are associated witha property path and have not been initiated. If there are more UIelements 46 in the UI 42 that have not been initiated, then the clientportion 22 a repeats steps 208, 212 and 216 for each of the additionalUI elements 46 that are not initiated. When all of the UI elements 46have been initiated, the client portion 22 a monitors (step 224) the UIelements 46 for user changes.

When the client portion 22 a registers (step 216) interest in a propertypath, the server portion 22 b, through the property/event interface 90,determines (step 228) the initial value for the registered propertypath. The server portion 22 b sends (step 232) the determined initialvalue to the client portion 22 a. The client portion 22 a updates (step236) the identified UI element 46 with the initial value. If there areany other UI elements 46 associated with the same property path, theclient portion 22 a updates (step 236) those elements 46 with theinitial value also. The server portion 22 b updates (step 240) the treestructure map 160 with the registration of interest for the propertypath, received from the client portion 22 a, and the determined initialvalue.

The client portion 22 a determines (step 244) whether the update of theUI element(s) 46 resulted in creating one or more additional UI elements46 (e.g., additional employees were added to the list). If one or moreadditional UI elements 46 were added, then the client portion 22 arepeats steps 208, 212 and 216 for each of the additional UI elements46. If no additional UI elements 46 are added, the client portion 22 amonitors (step 244) the UI elements 46 for user changes.

While monitoring (step 224) the UI elements 46, the client portion 22 adetermines (step 224) whether the user changed the value of an existingUI element 46. If the user does not change the value of an existing UIelement 46, then the client portion 22 a continues to monitor (step 224)the UI elements 46. If the user does change the value of an existing UIelement 46, then the client portion 22 a informs (step 248) the serverportion 22 b of the change. If there are any other UI elements 46associated with the same property path as the changed UI element 46, theclient portion 22 a also updates (step 236) those UI elements 46 withthe changed value and determines (step 244) whether any new UI elements46 are created as a result of the change.

Upon being informed (step 248) by the client portion 22 a, the severportion 22 b attempts to update (step 252), via the property/eventinterface 90, the value of the property 38 of the application component34 affected by the user change (i.e., the property 38 at the end of theproperty path associated with the user-interface element 46 the userchanged). The application 26 determines (step 253) whether to accept thechange or to veto the change. If the application 26 accepts the change,the application 26 changes the state (e.g., value) of the property 38 asrequested by the server portion 22 b and generates a change event. Theserver portion 22 b receives the change event and determines (step 260)whether the change corresponds to a property path in which the clientportion 22 a has interest and acts in response to that determination. Inone embodiment, the server portion 22 b inhibits sending a change eventto the client portion 22 a for the changed property 38, because theclient portion 22 a originated the change.

If the application 26 does not accept the change (e.g., vetoes thechange), the server portion 22 b generates (step 254) a special changemessage to change the value of the property path, as displayed on the UI42, back to the original (i.e., pre-user modification) value. The serverportion 22 b continues by sending (step 232) the change message with theoriginal value back to the client portion 22 a.

After the tree structure 160 has been updated (step 240), the serverportion 22 b continues to monitor (step 256) the propertiescorresponding to the tree structure map 160. If a state (e.g., value) ofa property changes, the server portion 22 b determines (step 260)whether the change corresponds to a property path in which the clientportion 22 a has interest. If the server portion 22 b determines (step260) the changed state of the property does not correspond to aregistered property path, the server portion 22 b continues to monitor(step 256) the states of properties corresponding to the tree structuremap 160. If the server portion 22 b determines (step 260) the changedstate of the property does correspond to a registered property path, theserver portion 22 b generates and sends (step 232) to the client portion22 a a change event for the corresponding property path. The clientportion 22 a updates (step 236) any UI elements 46 associated with theproperty path with the changed value.

The property connector API 22 also can be configured to provideadditional features. For one example, if in the system 54 of FIG. 3 theclient node 64 and/or page interface 112 (e.g., browser) is unable torun the client portion 22 a or support some or all of the UI elements 46required for the specific user-interface 42, then the property connectorAPI 22 can generate a proxy process (not shown). The proxy process canexecute on the server node 60, or on another server node 60′ (not shown)logically located between the client node 64 and the server node 60executing the application 26. The proxy process acts as a client portion22 a in as far as communications with the server portion 22 b, and actsas a standard server process, using an alternative, compatible protocol,to communicate with the client node 64.

For example, a system 54′ includes a client node 64′ that has an olderversion of a Web browser 112′ that is unable to support the clientprocess 22 a. The proxy process receives the interactive page 42 and thedynamic changes indicated by the property connector API 22 and, inreal-time, converts the page 42 and the dynamic changes into a staticpage 42′ that is compatible with the older version Web browser 112′. Theconverted static page 42′ includes traditional style links and inputboxes to replace the dynamic mouse events and text fields used with theclient portion 22 a. When the user clicks on a link, the client node 64′requests a new page 42′ from the proxy process. The proxy processinterprets this as a click on a portion of the interactive page 42, andif this results in a change to a state of a property, the proxy processsends the change to the state of the property to the server portion 22b. The proxy process then generates a new static page 42″, in real time,to represent the new UI state and sends the new page 42″ to the clientnode 64′.

FIG. 8 depicts an embodiment of the server portion 22 b′ of the propertyconnector API 22 configured to provide an additional feature ofexecuting an extension 270. The server portion 22 b′ includes a firstproperty path manager 86 a, a first property/event interface 90 a, asecond property/event interface 90 b, the extension 270 and an extensionmanager 274. The extension 270 includes extension components 278,analogous to the application components 34. The extension 270 is aprocess that augments the application 26, becomes an ‘extension’ of theapplication 26. Two exemplary extensions are a page extension and a formextension. To the client portion 22 a, the extension 270 acts like apart of the application 26. To the application 26, the extension 270acts like part of the client portion 22 a. The extension manager 274includes a second property path manager 86 b and an extension eventmanager 282.

A request to execute an extension 270 is included in the UI 42. The pageinterface 112 loads the UI 42 and when the client portion 22 aencounters the extension request, the client portion 22 a sends therequest to the server portion 22 b to initiate execution of theextension 270. An exemplary request command for a page extension is‘Session.PageView=newExtension(‘PageView’,‘App.Employee[]’,10)’. Withreceipt of this command, the server portion 22 b initiates execution ofthe named extension ‘PageView’ on the server node 60. In accordance withthe parameters of the command, the server portion 22 b initializes theextension 270 with the values ‘App.Employee[]’ and 10. The extension 270registers interest in the App.Employee[] property path with the propertypath manager 86 b, and is told of all members of this indexed property,and any changes.

The PageView extension 270 provides an indexed property Page[i], whichis an indexed property of ‘Page’ objects 278. Each Page object 278 inturn provides an indexed property ‘Item[j]’, which is an indexedproperty of items on the current page 42. The PageView extension 270allows the App.Employee property to be accessed via a number of pages 42a to 42 i, where i is the number of pages. For example the property path‘Session.PageView.Page[0].Item[0]’ is equivalent to property path‘App.Employee[0]’. The first employee is displayed on the first page.Similarly, the property path ‘Session.PageView.Page[1].Item[4]’ isequivalent to the property path ‘App.Employee[14]’ because after thefirst ten employees (the entered parameter was ten), the next tenemployees are displayed on a second page. The PageView extension 270also provides other properties such as NoPages, CurrentPage, NextPage,LastPage, and the like, to make it easy to build page based interfacesto applications 26 that do no themselves support multiple pages 42 a to42 i.

Another extension is the ‘Form’ extension. The form extension provides ameans for ‘batch processing’ of application data. The form extensionallows transactional input to an application 26. For example, a user mayfill in a form 42 a (not shown) displayed in a UI 42 and then cancel orsubmit the filled in form 42 a as a whole, instead of piecemeal data. Ifthe server portion 22 b′is configured with a form extension 270, theclient portion 22 a creates a form 42 a by a call toSession.newExtension. This command takes two mandatory parameters,‘String id’ and ‘String type’ and one optional parameter ‘String args’.The ‘String id’ parameter includes the name of the extension (e.g.‘myform’) and is in the format ‘Session.myform’. The ‘String type’parameter includes the type of the extension, which for a formextension, is in the format ‘Form’. The ‘String args’ parameter includesan optional argument string. For the form extension, the format is oneof ‘ ’ (i.e., null), ‘snapshot’, ‘weakchanges’ or ‘snapshot,weakchanges’. The snapshot and weakchanges modes are described in moredetail below.

The form extension 270 is configured to accept several methods. Onemethod is ‘submit( )’, which transmits all changed values to the formextension 270 to update the application 26. Another method is ‘refresh()’, which refreshes all values within the form 42 a, including changedones, to be the same as the corresponding application properties 38.Another method is ‘update( )’, which refreshes all of the unchangedvalues to be the same as the corresponding application properties 38.The method is useful for unconnected forms. Another method is ‘clear()’, which resets all changed values to null. This method is useful forcomplex forms. Another method is ‘clear(v)’, which resets all changedvalues to v.

The call to create a form 42 a is usually made in a script type UIelement to ensure that the form 42 a is initialized before UI elements46 using the form 42 a are displayed. The form 42 a is global and may beused anywhere on the page 42, not just inside the script UI element 46.An exemplary code used to create a form 42 a is as follows:

<div widget=“script”onstart=“invoke_server(this,‘Session.newExtension(\’F\‘,\’Form\)‘)’)”><table> <tr> <td><b>Employee</b></td> <td><b>Salary</b></td> <tr> <tbodystyle=‘display:none’ widget=‘iterator’ range=‘Session.F.App.Employee[]’><tr> <td><span widget=‘text’ variable=‘%itm.Name’>Name</span></td><td><input widget=‘value’ variable=‘%itm.Salary’></td> <tr> </tbody></table> <input type=“button” value=“Clear”onclick=“invoke_server(this,‘Session.F.clear(0)’)”> <input type=“button”value=“Reset” onclick=“invoke_server(this,‘Session.F.refresh( )’)”><input type=“button” value=“Submit”onclick=“invoke_server(this,‘Session.F.submit( )’)”> </div>

When the server portion 22 b′ is configured with a form extension 270,the property paths ‘Session.Form.App.Name’ and‘Session.Form.App.Employee[5].Salary’ have the same value as theproperty paths ‘App.Name’ and ‘App.Employee[5].Salary’. Any change to aproperty starting ‘Session.Form’ is recorded in the form extension 270and not applied to the application 26 until the client portion 22 ainvokes a Session.Form.submit( ) method. In one embodiment, the clientportion 22 a invokes a ‘Session.Form.submit( )’ when the user clicks ona UI element button labeled submit. Alternatively, the client portion 22a invokes a Session.Form.cancel( ) method, in which case nothing willchange.

The form extension 270 works by acting as a filter over other properties38. For example a form 42 a can be identified as ‘Session.Form’. Forexample, this form 42 a displays values associated with property pathssuch as ‘Session.Form.App.Name’, ‘Session.Form.App.Employee[2].Salary’and the like. There is no need to define what properties correspond to aform 42 a, as the properties 38 are associated dynamically as they arereferred to by UI elements 46 within the page 42.

By default, a form 42 a is connected and set to preservesChanges. Thatis, if an application property 38 changes during the lifetime of theform 42 a, the form 42 a reflects the change unless the user has alreadychanged the value. This also means that if the page 42 wishes to displaynew values in the form 42 a, then this will happen automatically (e.g.,iterator type UI elements 78 b or treeview type UI elements 78 g).

In various embodiments, the form 42 a can be set to different modes. Inone embodiment, the form 42 a may optionally be set to ‘snapshot’ mode,where it is unconnected and all values will be null until entered by theuser or the form 42 a is manually refreshed. In another embodiment, theform 42 a may also be optionally set to ‘weakchanges’ mode, wherechanges to values from the application 26 will overwrite changes made bythe user.

In one embodiment, if an application property 38 changes that is anancestor of a property 38 displayed on the form 42 a, and the form 42 ais connected or manually updated, then the dependent properties on theform 42 a are updated even if the user has changed them. For example, aform 42 a displays App.Employee[0].Name (=Fred) andApp.Employee[0].Salary (=100). If the user changes the salary to 200(e.g., Fred's salary), and then the application 26 changes whoApp.Employee[0] is (e.g. to Bill, Salary 50), then the form 42 acorrectly displays App.Employee[0].Name=Bill andApp.Employee[0].Salary=50, discarding the users original, and nowinvalid, user change. As a consequence, if ancestor properties change asa result of submitting a number of changes in a form 42 a, then it ispossible that some of the changes are discarded.

In some embodiments, data is not batched and sent to the server node 60all at once. For example, the updates can be transmitted to theapplication sequentially, or in a random order. The application 26reacts to the data as if it were entered all at the same time, due tothe interaction of the form extension 270 on the server node 60.

EQUIVALENTS

While the invention has been particularly shown and described withreference to several exemplary embodiments thereof, it will beunderstood by those skilled in the art that various changes in form anddetail may be made therein without departing from the spirit and scopeof the invention.

For example, although the methods and apparatus of the present inventionare described in the context of a Web server and Web client processcommunicating over the Internet, those skilled in the art will recognizethat the present invention also can be practiced in non-Web and/ornon-Internet embodiments. The invention also can be practiced over anyother type of network (e.g., telephone, cable, LAN, WAN, wireless,fiber), within the same physical computer system, or with portions ofthe invention (e.g. the application independent client process)operating in an Internet appliance or cable TV set-top box.

1. In a system including an application having a plurality ofcomponents, at least one component having a property, each propertybeing identified with an identifier, a method of associating an elementof a user-interface to a current state of a property, the user-interfacecreated independently of the application with which the user interfaceinteracts, the method comprising: (a) aassociating an element of auser-interface with a property path, the property path including aconcatenation of a plurality of identifiers, the concatenation ofidentifiers defining a path through a plurality of applicationcomponents to a property at the end of the concatenation; (b) mappingthe property path to a current state of the property at the end of thepath defined by the concatenation of identifiers to associate theelement of the user-interface with the current state of that property;(c) detecting a change in one of a plurality of states in anapplication, each state in the plurality corresponding to one of thestates mapped to an identifier in the concatenation of the propertypath; (d) examining each identifier in the concatenation of the propertypath in succession, starting with an identifier corresponding to thechanged one of the states of the plurality of states; (e) determiningfor a currently examined identifier, a new next state of a property witha name identical to the currently examined identifier; (f) re-mappingthe currently examined identifier to the new next state in response to achange in a currently mapped state; (g) repeating the steps of detectinga change in one of a plurality of states in an application and ofexamining each identifier in the concatenation of the property path insuccession, for each subsequent identifier in the concatenation ofidentifiers; and (h) updating the element of the user-interfaceassociated with the property path responsive to the detected change. 2.The method of claim 1 wherein step (b) further comprises: (b-1).examining each identifier in the concatenation of the property path insuccession; (b-2). determining, for the first identifier in theconcatenation of the property path, a second state of a property with aname identical to the first identifier, a component of the applicationcontaining that property becoming a root application component; (b-3).identifying, for the first identifier, a component of the application towhich the second state points as a current application component; (b-4).mapping the first identifier to the second state; (b-5). determining forthe next identifier in the concatenation of the property path, a nextstate of a property with a name identical to the next identifier locatedwithin the current application component; (b-6). identifying, for thenext identifier, a component of the application to which the next statepoints as a current application component; (b-7). mapping the nextidentifier to the next state; and (b-8). repeating steps e(b-5) trough(b-7) until the last identifier of the concatenation is examined to mapthe property path to the current state of the property with a nameidentical to the last identifier.
 3. The method of claim 1 wherein step(b) further comprises mapping the property path to an undefined state ifno property is found that corresponds to an identifier in the pluralityof identifiers in the concatenation.
 4. The method of claim 1 whereinstep (b) further comprises generating a node tree having a plurality ofnodes, wherein each node of the node tree represents a mapping of anidentifier to one of, a state of a property and an undefined state. 5.The method of claim 4 wherein the node tree represents a plurality ofproperty paths.
 6. The method of claim 1 further comprising the stepmonitoring a plurality of states within the application to detect achange in one of the states of the plurality of states, each state inthe plurality corresponding to one of the states mapped to an identifierin the concatenation of the property path.
 7. The method of claim 6wherein the step of monitoring further comprises receiving a propertychange event from a JAVABEAN-compatible component.
 8. The method ofclaim 6 further comprising re-mapping the property path to a new currentstate in response to detecting the change in one of the states of theplurality of states.
 9. The method of claim 6 further comprisingre-mapping the identifier the concatenation of identifiers to thechanged state in response to detecting the change in one of the statesof the plurality of states.
 10. The method of claim 1 further comprisingthe step of generating a property change message in response to a changein a state of a property corresponding to one of the identifiers in theconcatenation of the property path.
 11. The method of claim 1 furthercomprising the step of updating one or more user-interface elementsassociated with the property path with a new current state in responseto a change in the current state of the property.
 12. The method ofclaim 1 wherein step (g) further comprises terminating the repeating inresponse to the new next state being identical to a state currentlymapped for that currently examined identifier.
 13. The method of claim 1further comprising the step of monitoring a new plurality of stateswithin the application, the new plurality including the new next statesmapped to an identifier in the concatenation of the property path. 14.The method of claim 1 wherein the property path is a first property patand the concatenation of identifiers includes a wildcard identifier andfurther comprising: mapping a second property path to a first value; anddetermining a second value for the wildcard identifier in response tothe first value mapped to the second property path.
 15. The method ofclaim 14 wherein the step of determining the second value furthercomprises determining the second value such that replacing the wildcardidentifier of the first property path with the second value causes thecurrent state mapped to the first property path with the replacedwildcard identifier to be equal to the value mapped to the secondproperty path.
 16. The method of claim 1 further comprising dynamicallybinding the property path to one of the application components includingthe property corresponding to the current state mapped to that propertypath.
 17. The method of claim 1 further comprising transmitting to theapplication a request to update the current state of the property mappedto the property path associated with the element of the user-interfacein response to a user modification of the value.
 18. The method of claim17 further comprising inhibiting a property change message in responseto the application updating the current state of the property inresponse to the request to update.
 19. The method of claim 1 wherein theuser interface comprises an exemplary element associated with a propertypath including a wildcard identifier, the wildcard identifiercorresponding to an indexed property including an index value range froma minimum value to a maximum value, further comprising: generating anadditional element for each index value of the indexed property from theminimum value to the maximum value by copying the given elementassociated wit the property path; and associating a new property pathwith each add additional element.
 20. The method of claim 19 furthercomprising replacing the wildcard identifier associated with the givenelement with the corresponding index value of the additional element todefine the new property path.
 21. The method of claim 1 furthercomprising registering interest in the property path.
 22. The method ofclaim 1 wherein the step of mapping further comprises mapping one of theidentifiers in the concatenation of the property path to a state of aproperty corresponding to the one of the identifiers.
 23. The method ofclaim 1, wherein set (a) further comprises associating a component inthe application with a property path including a concatenation of aplurality of identifiers.
 24. The method of claim 1 further comprisingthe step of invoking a method responsive to an update to an element ofthe user-interface.
 25. The method fo claim 1 further comprising thestep of providing, to a method, a property path identifying a componentin the application.
 26. A system for associating an element of auser-interface to a current state of a property of an application, theapplication having a plurality of components, at least one componenthaving a property, each property being identified with an identifier,the user-interface created independently of the application with whichthe user interface interacts, the system comprising: a propertyconnector module configured: (1) to identify an association between anelement of a user-interface and a property path, the property pathincluding a concatenation of a plurality of identifiers defining a paththrough a plurality of application components to a property at the endof the concatenation; (2) to map the property pat to a current state ofthe property at the end of the path defined by the concatenation ofidentifiers, thereby associating the element of the user-interface withthe current state of that property; (3) to detect a change in one of aplurality of states in an application, each state in the pluralitycorresponding to one of the states mapped to an identifier in theconcatenation of the property path, (4) to examine each identifier inthe concatenation of the property path in succession, starting with anidentifier corresponding to the changed one of the states of theplurality of states: (5) to determine for a currently examinedidentifier, a new next state of a property with a name identical to thecurrently examined identifier; (6) to re-map the currently examinedidentifier to the new next state in response to a change in a currentlymapped state; (7) to repeat steps (3) through (6) for each subsequentidentifier in the concatenation of identifiers, and (8) to update theelement of the user-interface associated with the property pathresponsive tote detected change.
 27. The system of claim 26 wherein theproperty connector module is further configured to: (2-1). examine eachidentifier in the concatenation of the property path in succession;(2-2). determine, for the first identifier in the concatenation of theproperty path, a second state of a property with a name identical totefirst identifier, a component of the application containing thatproperty becoming a root application component; (2-3). identify, for thefirst identifier, a component of the application to which the secondstate points as a current application component; (2-4). map the firstidentifier to the second state; (2-5). determine, for the nextidentifier in the concatenation of the property path, a next state of aproperty with a name identical to the next identifier located within thecurrent application component; (2-6). identify, for the next identifier,a component of the application to which the next state points as acurrent application component; (2-7). map the next identifier to thenext state; and (2-8). repeat steps (2-5) through (2-7) until the lastidentifier of the concatenation is examined to map the property path tothe current state of the property with a name identical to the lastidentifier.
 28. The system of claim 26 wherein the property connectormodule is further configured to map the property path to the currentstate further comprises mapping the property path to an undefined stateif no property is found that corresponds to an identifier in theplurality of identifiers in the concatenation.
 29. The system of claim26 wherein the property connector module is further configured togenerate a node tree having a plurality of nodes, wherein each node ofthe node tree represents a mapping of an identifier to one of, a stateof a property and an undefined state.
 30. The system of claim 29 whereinthe node tree represents a plurality of property paths.
 31. The systemof claim 26 wherein the property connector module is further configuredto monitor a plurality of states within the application to detect achange in one of the states of the plurality of states, each state inthe plurality corresponding to one of the states mapped to an identifierin the concatenation of the property path.
 32. The system of claim 31wherein the property connector module is further configured to receive aproperty change event from a JAVABEAN-compatible component.
 33. Thesystem of claim 31 wherein the property connector module is furtherconfigured to re-map the property path to a new current state inresponse to detecting the change in one of the states of the pluralityof states.
 34. The system of claim 31 wherein the property connectormodule is further configured to re-map the identifier the concatenationof identifiers to the changed state in response to detecting the changein one of the states of the plurality of states.
 35. The system of claim26 wherein the property connector module is further configured togenerate a property change message in response to a change in a state ofa property corresponding to one of the identifiers in the concatenationof the property path.
 36. The system of claim 26 wherein the propertyconnector module is further configured to update one or moreuser-interface elements associated with the property path with a newcurrent state in response to a change in the current state of theproperty.
 37. The system of claim 26 wherein the property connectormodule is further configured to terminate the repeating in response tothe new next state being identical to a state currently mapped for thatcurrently examined identifier.
 38. The system of claim 26 wherein theproperty connector module is further configured to monitor a newplurality of states within the application, the new plurality includingthe new next states mapped to an identifier in the concatenation of theproperty path.
 39. The system of claim 26 wherein the property path is afirst property path and the concatenation of identifiers includes awildcard identifier and the property connector module is fartherconfigured to: map a second property path to a first value; anddetermine a second value for the wildcard identifier in response to thefirst value mapped to the second property path.
 40. The system of claim39 wherein the property connector module is further configured todetermine the second value such that replacing the wildcard identifierof the first property path with the second value causes the currentstate mapped to the first property path with the replaced wildcardidentifier to be equal to the value mapped to the second property path.41. The system of claim 26 wherein the property connector module isfurther configured to dynamically bind the property path to one of theapplication components including the property corresponding to thecurrent state mapped to that property path.
 42. The system of claim 26wherein the property connector module is further configured to transmitto the application a request to update the current state of the propertymapped to the property path associated with the element of theuser-interface in response to a user modification of the value.
 43. Thesystem of claim 42 wherein the property connector module is furtherconfigured to inhibit a property change message in response to theapplication updating the current state of the property in response tothe request to update.
 44. The system of claim 26 wherein the userinterface comprises an exemplary element associated with a property pathincluding a wildcard identifier, the wildcard identifier correspondingto an indexed property including an index value range from a minimumvalue to a maximum value, and the property connector module is furtherconfigured to: generate an additional element for each index value ofthe indexed property from the minimum value to the maximum value bycopying the given element associated with the property path; andassociate a new property path with each additional element.
 45. Thesystem of claim 44 wherein the property connector module is furtherconfigured to replace the wildcard identifier associated with the givenelement with the corresponding index value of the additional element todefine the new property path.
 46. The system of claim 26 wherein theproperty connector module is further configured to register interest inthe property path.
 47. The system of claim 26 wherein the propertyconnector module is further configured to map one of the identifiers inthe concatenation of the property path to a state of a propertycorresponding to the one of the identifiers.
 48. The system of claim 26further comprising: a client node including: the user interface havingone or more elements; and a client portion of the property connectormodule.
 49. The system of claim 26 further comprising: a server nodeincluding: the application; and a server portion of the propertyconnector module.